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Nanometer-Thick Conjugated Microporous Polymer Films for Selective and Sensitive Vapor-Phase TNT Detection
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  • Venkata Suresh Mothika*
    Venkata Suresh Mothika
    Macromolecular Chemistry Group, Bergische Universität Wuppertal, Gaußstraße 20, 42119 Wuppertal, Germany
    *E-mail: [email protected]
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    Orcidhttp://orcid.org/0000-0002-3084-1279
  • André Räupke
    André Räupke
    Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany
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  • Kai Oliver Brinkmann
    Kai Oliver Brinkmann
    Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany
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  • Thomas Riedl
    Thomas Riedl
    Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany
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  • Gunther Brunklaus
    Gunther Brunklaus
    Institut für Physikalische Chemie, Westfälische Wilhelms-Universität, Corrensstr. 46, D-48149 Münster, Germany
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    Orcidhttp://orcid.org/0000-0003-0030-1383
  • Ullrich Scherf
    Ullrich Scherf
    Macromolecular Chemistry Group, Bergische Universität Wuppertal, Gaußstraße 20, 42119 Wuppertal, Germany
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ACS Applied Nano Materials

Cite this: ACS Appl. Nano Mater. 2018, 1, 11, 6483–6492
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https://doi.org/10.1021/acsanm.8b01779
Published October 16, 2018

Copyright © 2018 American Chemical Society. This publication is licensed under these Terms of Use.

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Abstract

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Conjugated microporous polymer (CMP) thin films often show fast and amplified signal response and potential for developing portable sensing devices. Here, we elucidate electrochemical generation of three CMP thin films and their fluorescence response to trinitrotoluene (TNT). A tetra(carbazolylphenyl)ethylene monomer TPETCz-derived CMP thin film (PTPETCz, SBET: 930 m2/g) displayed fluorescence (λmax = 525 nm) quenching to nearly 95% in 3 min, when the CMP film is exposed to 33 ppb TNT vapors. Interestingly, PTPETCz is highly sensitive (30% quenching) to TNT vapors of low concentrations (5–10 ppb) and also remarkably selective toward TNT compared to other analytes. In contrast, an only mere response was observed when a nonporous monomer TPETCz-film was exposed to 0.2 ppm TNT. So, the microporosity and extended π-conjugation of the polymer facilitating suitable host–guest interactions is found to be essential toward highly sensitive detection of TNT. Fluorenone-cored CMP thin films (PFLCz) showed no response, while PTPEFLCz containing both tetraphenylethylene and fluorenone structural units showed nearly 70% of emission quenching in the presence of 0.2 ppm TNT. Therefore, the presence of electron-donating TPE core is a prerequisite for efficient photoinduced electron transfer from polymer to nitroarenes.

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1. Introduction

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Research efforts on trace-level detection of explosive chemical vapors are rapidly increasing owing to its importance in environment and defense/security applications. (1,2) Several explosive sensors based on small molecules, conjugated polymers, self-assembled organic nanomaterials, and metal–organic frameworks have been studied for both solution and vapor-phase explosives detection up to detection limits of part per trillion (ppt). (3−14) The microporous environment of metal/organic frameworks enabling fast diffusion of analytes and effective host–guest interactions was key for the enhanced sensitivity, while extended π-conjugation in conjugated polymers was shown to be a very promising feature for amplified signal transduction. (11−14) In this context, conjugated microporous polymers (CMPs) (15−21) featuring both microporosity and extended π-conjugation with large surface area are unique for fluorescence-based sensing of explosive vapors. Efficient exciton migration along the polymer network and an excellent analyte diffusion opportunity can be useful for fast and amplified fluorescence response. (22−24) Moreover, CMPs are thermally and chemically stable due to strong C–C linkages between connecting building blocks. (25−29) Several chemically synthesized CMP powders have been studied for fluorescence-based sensing of chemical analytes; (30−36) however, their limited processability often restricts device fabrication. For an example, silsesquioxane-based porous polymers or porphyrin networks were solution-processed onto lightweight paper or thin-layer chromatography (TLC) plate substrates and used as portable sensors for chemical sensing. Nevertheless, they use expensive Pd(0) catalysts, and additional efforts were needed to remove trace catalyst impurities and to control film thickness. (37−39)
Recently, the electro-oxidative polymerization technique for synthesizing CMP thin films gained significant attention. (40−44) This catalyst-free technique is cost-effective and can provide highly pure CMPs in short times with excellent control over film thickness. These films can be grown on a large variety of electrodes including flexible substrates thus enabling device fabrication. (45−47) Electropolymerization approaches of carbazolyl and thienyl building blocks into CMP thin films for various applications were studied recently. (48) The electrochemical sensing of nitroaromatic compounds (NACs) using various CMP thin films with detection levels of several micrograms per milliliter was also reported. (49) Tetraphenylethylene (TPE)-based materials show aggregation-induced emission (AIE) and have been widely studied for sensing of various small molecules including explosives. (50−55) Recently, fluorescence quenching of CMP thin films (PTPETPOcCz, SBET = 2170 m2/g) by TNT in aqueous solution (50 ppm) was studied by us, (56) while Jiang et al. reported polyTPECz-based thin films showing fluorescence quenching response to 50 ppm 2,4,6-trinitriphenol (TNP) solutions with good selectivity, low detection limits, and proper fluorescence retention after the analyte was washed out. (57) Solution-phase sensing methods are, in principle, applicable to environmental safety devices, but with certain limitations due to the use of liquid systems, although good performance can be achieved. Having encouraging results of solution-phase optical sensing based on thin films of TPE-cored networks from our previous studies, we now propose to use PTPETCz (SBET = 930 m2/g) thin films with their strongly greenish-cyan emission (λmax: 525 nm) also for vapor-phase explosive sensing. Vapor-phase sensing can be distinctly different from solution-phase processes, since the nitroaromatic compounds possess quite different vapor pressures. Generally, vapor-phase sensing may be more relevant to real-time sensing. (58)PTPETCz used in the presented study is higher fluorescent if compared to the previously studied PTPTCz (49) and, believably, it may act as superior-performing optical sensor. There are relatively few reports on electrogenerated CMP thin films for vapor-phase sensing of explosives. (59) TPBCz-CMP films were already studied for vapor-phase sensing with good performance, (60) and the further development of such materials may be important for homeland security applications. CMP thin films prepared by other techniques were also shown to be promising vapor-phase sensors. (58,59,62) The present work on electrogenerated PTPETCz films also documents a very encouraging sensing performance with high sensitivity and short response time. The electropolymerization approach represents a favorable approach for creating high-quality CMP thin films that are suitable for device fabrication (as reported, e.g., by Jiang et al. and by Ma et al.). (45−47) However, reports on electropolymerized CMP thin films showing high sensitivity for trace-level trinitrotoluene (TNT) vapors are scarce. We recently reported CMP thin films for vapor-phase sensing of NACs including sensing of 5 ppb TNT based on efficient fluorescence quenching. (59) In our new experiments, the PTPETCz emission is strongly quenched (95%) when exposed to 33 ppb of TNT vapor in 3 min and also showed excellent selectivity if compared to the response to various other nitroaromatic analytes (Scheme 1). PTPETCz showed remarkable selective response to TNT vapors among the nitroaromatic compounds studied. To our surprise, an appreciable fluorescence response (30% quenching) even to lower concentrations (5–10 ppb) of TNT vapors is observed. We further studied the dependence between film thickness and sensitivity to TNT vapors for the CMP films. Intriguing AIE property of TPE cored materials was shown to be responsible for its efficient sensing properties. (50−55,61) The PTPETCz-based sensing response may be similarly explained. CMP thin films grown from the fluorenone-cored carbazolyl derivative FLCz exhibited no remarkable response to TNT. In contrast, a CMP thin film prepared from a mixture of monomers 1,1,2,2-tetra[4-(carbazol-9-yl)phenyl]ethene (TPETCz) and 2,7-di(carbazol-9-yl)-fluoren-9-one (FLCz) displayed appreciable responses to TNT in the vapor phase. Although several CMP-based thin films have been reported for trace-level explosive detection, (58,59,62) we believe that the present work represents a promising new example among the already reported systems that have been studied for vapor-phase TNT sensing.

Scheme 1

Scheme 1. Schematic Illustration of the Electropolymerization of TPETCz into Fluorescent PTPETCz Thin Film, and the Fluorescence Quenching in the Presence of Trace TNT Vapors
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2. Experimental Section

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Materials and Methods

All reagents and chemicals required have been purchased from commercial chemical suppliers, unless stated. TPETCz is synthesized according to a literature procedure. (56)1H NMR spectra are measured using Bruker Avance III 400 MHz machine. APCI mass spectra are measured on a Bruker Daltronik microTOF system (KrF*-Laser ATLEX-SI, ATL). Bulk polymers synthesized by the chemical oxidation method are purified by washing with supercritical CO2 in a Tousimis Samdri-795 system. Bulk polymer samples and thin films are activated on a Belprep-vac II at 140 °C and ∼2 Pa over 10 h for adsorption measurements. Kr adsorption measurements are performed using a BEL Japan Inc. Belsorp-max system at 77 K in the relative pressure range of 0–0.6, P0 = 1 atm. Ionization potential measurements are performed with atmospheric pressure ultraviolet photoelectron spectroscopy System (Riken Keiki AC-2). Thermogravimetric analyses (TGA) are recorded at a Mettler Toledo TGA/DSC1 STAR machine under Ar atmosphere with a heating rate of 5 °C per min. UV/Vis absorption and Fourier transform infrared (FTIR) measurements are performed using JASCO V-670 and FTIR-4200 machines, respectively. Photoluminescence (PL) is measured using a HORIBA Scientific FluoroMax-4 spectrofluorometer connected to a QuantaPhi integrating sphere for determination of PL quantum yields. Photoluminescence measurements for sensing experiments are recorded using diode-pumped solid-state laser photoexcitation (λ = 355 nm, 11 mW/cm2) coupled into a monochromator and detected with a cooled charge-coupled device camera (Princeton Instruments). Atomic force microscopy (AFM) images of the thin films are obtained on a Bruker diInnova system operated in tapping mode; the surface roughness is extracted from the topography images.

Solid-State NMR Measurements

13C{1H} cross-polarization magic-angle spinning (CPMAS) spectra were recorded at 50.33 MHz using a Bruker AVANCE III 200 NMR spectrometer with a contact time of 2.5 ms, averaging 17 408 transients at a relaxation delay of 2 s; the contact pulse was ramped from 70% to 100% of the optimized power level of 55 W. All experiments were performed at room temperature (air-conditioned to 20 °C), employing a standard Bruker 2.5 mm double resonance MAS probe spinning at 20 kHz, typical π/2-pulse lengths of 3.5 μs (reflecting a radiofrequency (RF) field strength of 71.4 kHz) and SPINAL64 proton decoupling (200.15 MHz; 10π/12 pulse set to 5.8 μs) at rather modest power levels of 32 W (13C) and 20 W (1H), respectively. The 13C spectra were referenced with 1-13C and 15N isotope-enriched solid α-glycine as secondary standard (176.0 ppm for 13C_carbonyl). In addition, the line width of the 13C_carbonyl peak served as internal check for proper adjustment of the magic angle.

Electropolymerization

Thin film generation follows similar procedure as reported by our group earlier. (40,43,49) Monomer solutions (0.1 mM) are prepared in dichloromethane/acetonitrile (4:1) with 0.1 M tetrabutylammonium perchlorate (TBAP) as supporting electrolyte. A three-electrode cell connected to electrochemical workstation PAR VersaSTAT 4 is used under Ar atmosphere at 25 °C. Indium tin oxide (ITO) plates are used as working electrode (WE) combined with a platinum counter electrode (CE) and Ag°/AgNO3 (0.1 M AgNO3, 0.6 V vs normal hydrogen electrode (NHE), nonaqueous reference) as reference electrode (RE). Potentiostatic regimes are applied for generating porous polymer films on the ITO electrodes. For sensing experiments the films are grown by applying five cyclic voltammograms (CVs) between −0.2 and 1.1 V with a scan rate of 0.1 V s–1. Thicker films used for gas adsorption measurements are prepared by the chronoamperometry method by applying a constant potential of 1.1 V for 20 min followed by a discharging step at 0 V for 60 s to discharge the deposited films. Free-standing thin films are delaminated from the electrodes, dried after rinsing with CH3CN and CH2Cl2, and used for Kr adsorption measurements. The films are activated at 140 °C prior to the adsorption measurements.

Synthesis of 2,7-Di(carbazol-9-yl)-fluoren-9-one (FLCz)

2,7-Dibromo-9H-fluoren-9-one (1 g, 2.94 mmol), 9H-carbazole (7.34 mmol, 1.22 g), 2,2′-bipyridyl (229.4 mg, 1.47 mmol), CuI (1.297 g, 7.34 mmol), and K2CO3 (2 g, 14.7 mmol) are degassed in a double-neck flask and purged with Ar three times. To this mixture o-dichlorobenzene (30 mL) is added, and the batch is stirred at 180 °C under dark conditions for 48 h. Next the mixture is cooled to room temperature, filtered, and washed with dichloromethane several times. The filtrate is concentrated under reduced pressure, and the crude product is purified by column chromatography using chloroform/tetrahydrofuran (THF)/hexane (9:0.5:0.5) as eluent. Finally the product is recrystallized from a cyclohexane/chloroform (1:1) mixture. Red needlelike crystals are obtained after 3 d. Yield: 0.66 g (44%). 1H NMR (400 MHz, CDCl3): δ = 8.20 (d, 4 H), 8.0 (t, 2 H), 7.89 (d, 2H), 7.82 (d, 2H), 7.50 (m, 8 H), 7.37 (d, 4 H) ppm; 13C NMR (600 MHz, CDCl3) δ: 191.8, 142.28, 140.45, 139.01, 136.29, 133.07, 126.23, 123.75, 123.11, 121.74, 120.39, 109.72. Mass spectrometry (MS) atmospheric pressure chemical ionization (APCI) calcd for C37H23N2O: 511.1805, found m/z = 511.1808 (M+).

Synthesis of PTPETCz Bulk

It was synthesized using similar procedure reported by Scherf et al. (56) and obtained as pale green solid.

Synthesis of PFLCz Bulk

FLCz (0.12 mmol, 61 mg) is dissolved in 15 mL of dry chloroform and added dropwise to a suspension of FeCl3 (0.66 mmol, 108 mg) and stirred for 24 h at room temperature. To this mixture 100 mL of methanol is added and stirred for 1 h to precipitate the polymer. Precipitates are collected by filtration and washed thoroughly with methanol. Further, the powders are treated with concentrated HCl (35%) for 2 h and washed with water and methanol thoroughly. Compounds are purified by Soxhlet extraction with THF and methanol followed by supercritical CO2 washing (as described before) as final purification. (63)PFLCz is obtained as a red solid, yield: 48 mg (78%)

Synthesis of PTPEFLCz Bulk

TPETCz (0.12 mmol, 116 mg) and FLCz (0.12 mmol, 61 mg) are dissolved in 30 mL of dry chloroform and added dropwise to a suspension of FeCl3 (1.32 mmol, 216 mg), and the mixture is stirred for 24 h at room temperature. To this mixture 200 mL of methanol is added and stirred for 1 h to precipitate the polymer. The precipitates are collected by filtration and washed thoroughly with methanol. Further, the powder is treated with concentrated HCl (35%) for 2 h and washed with water and methanol thoroughly. The product is finally purified by Soxhlet extraction with THF and methanol followed by supercritical CO2 washing. PTPEFLCz is obtained as orange-red solid, yield: 87 mg (73%).

3. Results and Discussion

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Electropolymerization and Kr Adsorption

1,1,2,2-Tetra[4-(carbazol-9-yl)phenyl]ethene (TPETCz) is prepared in a procedure previously followed by our group, (56) while the 2,7-di(carbazol-9-yl)-fluoren-9-one (FLCz) monomer is synthesized in a condensation reaction of 2,7-dibromo-fluoren-9-one and carbazole under reflux conditions (see Supporting Information for details). Initially, the electrochemical behavior of the monomers is studied using 0.1 mM solution of the corresponding monomer in CH2Cl2/CH3CN (4:1) mixture with 0.1 M TBAP as supporting electrolyte. Figure 1a shows the first CV cycle of TPETCz, FLCz, and their 1:1 mixture (TPETCz/FLCz). TPETCz displays first reversible oxidation peak at ∼0.9 V, which can be attributed to the formation of stable radial cations at the TPE cores, and this signal was also observed for TPETCz/FLCz. In addition, monomers TPETCz, FLCz, and TPETCz/FLCz (1:1 mixture) exhibited irreversible oxidation peak at 1.1 V, which can be assigned to the oxidation of carbazole moieties of the monomers. Figure 1b–d displays the cyclic voltammograms of electro-oxidation and polymerization of TPETCz, FLCz, and TPETCz/FLCz with an applied oxidation potential of 1.1 V up to 20 cycles to form CMP thin films PTPETCz, PFLCz, and PTPEFLCz, respectively. For PTPETCz, it can be seen that starting from the second electrochemical cycle reversible peaks of charging and discharging are developed in the potential range from 0.5 to 0.8 V with gradual rise in current with increasing cycle number. This gradual rise in the current with increasing sweep cycle number reflects continuous growth of the polymer films at the electrode (ITO). In monomer-free solution the as-grown electrogenerated CMP films showed two reversible peaks for different scan rates from 0.005 to 0.2 V s–1 as evidence for charging/discharging processes in the polymers through reversible radical cation/dication formation (Figure S1). Further, a linear relationship between peak current and scan rate is observed, suggesting deposition of uniform, electroactive polymer deposits on the electrode. Similar polymer film growth characteristics are observed for FLCz and TPECz/FLCz (Figure S1). It can be noted that polymer growth is uniform throughout the ITO electrodes with a continuous coverage of the electrode surface. Formation of CMP thin films is evident from the FTIR spectra: New bands around 744 cm–1 correspond to the C–H bending vibration mode of N-substituted carbazoles that are present in polymer PTPETCz films; similar bands are also observed for PFLCz and PTPEFLCz. Additional bands around 802 cm–1 appeared for all polymers and represent C–H bending vibrations of 3- or 6-substituted carbazoles, thereby demonstrating the formation of “C–C” linkages between the carbazole moieties (Figure S2). Figures 2a & S3 shows the AFM images of three different CMP films grown by applying five cyclovoltammetric cycles. The thicknesses are calculated from the topography images to be 15, 38, and 19 nm for PTPETCz, PFLCz, and PTPEFLCz with an average roughness of 3.7, 7.5, and 4.5 nm, respectively. The low roughness values imply that the thin films are best suited for device fabrication.

Figure 1

Figure 1. (a) CVs of monomers (0.1 mM) TPETCz (black), FLCz (red), and their 1:1 mixture (TPECz/FLCz) (blue) in dichloromethane/acetonitrile (4:1) containing 0.1 M TBAP, ITO electrodes, potential range 0–1.5 V. (b–d) First 20 consecutive CV cycles showing electropolymerization and growth of CMP thin films of (b) PTPETCz, (c) PFLCz, and (d) PTPEFLCz, ITO electrodes, prepared from corresponding monomer (0.1 mM) solutions containing 0.1 M TBAP.

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Figure 2

Figure 2. (a) AFM images of CMP thin film of PTPETCz grown over five CV cycles and (b, c) digital images of free-standing PTPETCz or PFLCZ thin films, respectively. Kr gas adsorption isotherms of (d) CMP thin films prepared by electropolymerization and (e) CMP powders synthesized by chemical oxidation with FeCl3; PTPETCz (navy blue), PFLCz (green), and PTPEFLCz (black), all measured at 77 K.

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Free-standing polymer thin films necessary for porosity measurements are prepared using the chronoamperometry method by applying a constant oxidation potential of 1.1 V for 20 min followed by treatment at 0 V for 60 s to discharge the deposited films (Figure 2b,c). These free-standing CMP films were room-temperature-dried and used for Kr adsorption measurements. Prior to this, the thermal stability of the thin films is studied (all films have been dried by heating under vacuum at 140 °C). As shown in Figures S4–S6, initial weight loss (<2%) can be attributed to trapped solvents. All the films showed no further weight loss up to 200 °C, and further heating results in slow loss of nearly 30% mass until 650 °C. All the CMP thin films were activated at 140 °C ensuring to remove guest solvent molecules under vacuum prior to Kr gas adsorption measurements. Commonly, nitrogen gas sorption measurements are used for porous CMP materials to determine the specific surface area. However, electrogenerated CMPN thin films are generally obtained in small amounts and are not suited for nitrogen measurements, mainly due to the higher vapor pressure of N2 at 77 K. In contrast, Kr with its low saturation pressure (1.63 Torr) at 77 K facilitates determination of pressure changes with greater precision even for low amounts materials such as thin films. Therefore Kr is used for the determination of Brunauer–Emmett–Teller (BET) surface area of thin films. (64) Kr adsorption measurements of PTPETCz, PFLCz, and PTPEFLCz at 77 K up to a relative pressure (P/Po) of 0.6 showed type-I uptake profiles with higher uptake in the low-pressure region thus suggesting a microporous nature of the polymer thin films (Figure 2d). No characteristic hysteresis loop was observed in the pressure range of 0.3–0.6 P/Po for all CMP films (Figure S7). However, in the low-pressure region, the desorption process did not follow the adsorption path and showed a slight hysteresis; this may be attributed to a restricted access to the pores in microporous polymers. (65) The maximum gas uptake is observed to be 258, 133, and 142 mL/g, respectively. Application of the BET model on the Kr adsorption isotherms yielded surface areas of 930, 504, and 509 m2/g for PTPETCz, PFLCz, and PTPEFLCz, respectively; the corresponding BET constants and fitting parameters are shown in Figure S8. For comparison with the thin-film results, PTPETCz, PFLCz, and PTPEFLCz bulk CMPs are also synthesized by chemical oxidation using FeCl3 as oxidizing agent from the corresponding monomers at room temperature (see Experimental Section). To avoid collapse of porosity during conventional activation methods, CMP powders are desolvated using the supercritical CO2 drying method before further characterization. Figures S9 and S10 show the FTIR spectra of all bulk polymers along with those of the corresponding monomers. Stretching vibrations at 1597 (νC═C) and 1720 cm–1 (νC═O) confirm the presence of tetraphenylethylene or fluorenone moieties in PTPETCz, or PFLCz, or PTPEFLCz bulk CMPs. Also, a band around 746 cm–1 corresponding to the C–H bending vibration mode of N-substituted carbazoles is present in monomer TPETCz and polymer PTPETCz bulk; a similar band is observed for FLCz and PFLCz bulk. New bands around 800 cm–1 that appeared for all polymers correspond to C–H bending vibrations of 3- or 6-substituted carbazoles (not in TPETCz), thereby demonstrating the formation of C–C linkages between the carbazole moieties. Further on, the bulk polymers were characterized by 13C–CP/MAS solid-state NMR spectroscopy: A peak at 189 ppm can be assigned to the carbonyl carbon of fluorenone moiety present in the polymers PFLCz and PTPEFLCz bulk. The peaks in the range of 110–140 ppm can be ascribed to the aromatic C present in polymers (Figures S11 and S12). Thermogravimetric analysis (TGA) of PTPETCz, PFLCz, and PTPEFLCz bulk showed no apparent weight loss up to 300 °C thus suggesting appreciable thermal stability of all polymers; a steady weight loss until 500 °C and up to 70% (Figures S13–15) total weight loss on further heating is observed. Kr gas adsorption of bulk CMPs also showed type-I uptake profiles with final gas uptake of 475, 226, and 278 mL/g (Figure 2e) for PTPETCz, PFLCz, and PTPEFLCz bulk, respectively, suggesting their microporous nature. Application of the BET model on these Kr isotherms provided surface areas of 1375, 836, and 902 m2/g for PTPETCz, PFLCz, and PTPEFLCz bulk, respectively, and the corresponding BET constants and fitting parameters are shown in Figure S16. The BET surface areas as calculated from Kr gas adsorption measurements of the thin films were lower if compared to the corresponding bulk CMP powders. On the one hand, FeCl3-assisted oxidative coupling may lead to a higher cross-linking density of the building blocks and, as a consequence, to a microporous network with higher BET surface area. On the other hand, electropolymerization probably leads to a reduced cross-linking density, probably due to the preferential formation of dimeric carbazolic linkages.

Photophysical Studies

On the one hand, monomer TPETCz shows aggregation-induced emission (AIE) in the solid state at λmax = 470 nm due to restricted rotation of the phenyl rotors of the TPE core (Figure S17), while it is practically nonfluorescent in solution, a widely known phenomena in literature. (55) On the other hand, FLCz shows red emission (λmax = 637 nm) in the solid state (Figure S17) due to the presence of the fluorenone chromophore (n-π* transition). We studied the absorption and emission spectra of monomer FLCz in solvents of varying polarity to understand if the emission is dominated by intramolecular charge transfer (ICT). FLCz did not show appreciable changes in the absorption spectra with the variation of the solvent polarity (Figure S18). The emission spectra showed maxima at ca. 585 nm (in toluene, THF) which are red-shifted to 630 nm in dichloromethane, chloroform, and acetonitrile (Figure S18). This indicates some ICT character for the derivatives where the fluorenone unit is in conjugation with other aromatic substituents. The emission behavior indicates an excited-state stabilization with increasing solvent polarity. (66) However, the emission shifts are moderate, pointing for a less distinct ICT character for the FLCz emission. CMP films grown over five oxidative potential cycles for PTPETCz, PFLCz, or PTPEFLCz generation showed a main absorption band peaking at ∼310 nm with a shoulder at 370 nm that is assigned to the π–π* transition of bicarbazole moieties (Figure S19). In case of the fluorenone-containing CMP thin films (PFlCz and PTPEFlCz), a weak absorption band at longer wavelengths in the range of 450–550 nm should represent n−π* transitions. However, in case of PTPETCz thin films (fluorenone-free), an observed weak absorption tailing into the longer wavelength region may be due to light scattering. Therefore, we selected an excitation wavelength of 355 nm for the fluorescence quenching studies. PTPETCz, PFLCz, and PTPEFLCz films showed greenish-cyan (strong), red (weak), and orange-red (moderate) emission peaking at 525, 621, and 608 nm (λex= 355 nm), respectively (Figure S19), with photoluminescence quantum yields (PLQYs) of 4.0%, 0.5%, 1.9%, respectively. A similar emission trend is observed for the PFLCz bulk material when dispersed in solvents of various polarities as seen for the FLCz monomer (Figure S20). The network structure of the π-extended, electron-rich CMPs allows for an efficient exciton migration along polymer strands, the microporosity for an effective diffusion of guest molecules into the porous network; these features make CMPs promising for optical sensing of suited analytes, particularly electron-deficient species such as nitroaromatic compounds.

Optical Sensing of TNT

With this in mind, we tested the sensing ability of fluorescent PTPETCz (thickness: 15 nm) against TNT as analyte, an electron-deficient compound used as explosive. Prior to this, the work functions of all CMP films grown over 50 cycles were determined using atmospheric pressure ultraviolet photoelectron spectroscopy (UPS). The work functions are found to be 5.54, 5.4 and 5.55 eV (Figures S21, S22, and S23), respectively. The lowest unoccupied molecular orbital (LUMO) levels are calculated from the reduction potentials of the CMP thin films grown by electropolymerization in cyclic voltammetry measurements (see Supporting Information for details). From these data, the LUMO levels are estimated as −3.55, −3.61, and −3.60 eV for PTPETCz, PFLCz, and PTPEFLCz, respectively. These positions of the HOMO/LUMO energy levels for all CMP films in relation to the energy levels of the studied nitroarene analytes are depicted in Figure S24. For the sensing experiments a dual-chamber system connected with a laser diode for excitation is used to study the optical response of the CMP films toward TNT. All the sensing experiments are performed with films grown over five oxidative cycles. Different concentrations of TNT are exposed to the films on ITO, and simultaneous changes in emission spectra are recorded periodically over time. PTPETCz initially shows constant emission at 525 nm (λex = 355 nm); however, on exposure to TNT (33 ppb) gradual decrease in the emission intensity is observed with time, and an emission quenching of 73% is observed within 60 s. Remarkably, 95% emission quenching of PTPETCz is detected after 3 min (Figure 3a). Emission quenching is also evident for the human eye; please see the photographs of a PTPETCz film before and after TNT exposure (inset of Figure 3a and Figure S25). It is important to emphasize that the microporosity of PTPETCz plays a critical role along with extended π-conjugation for optical sensing with fast response time. Hereby, the microporosity (<1 nm) supports the vapor-phase diffusion of TNT molecules into the CMP network. Mesoporosity of hierarchical porous materials such as mesoporous silica is discussed as preferred scenario for mass transport and diffusion, especially in solution. (67) In the gas/vapor phase, the dominant microporosity of the CMPs should properly facilitate the diffusion of TNT molecules and provides a confined environment, where possible one-to-one host–guest interactions between polymer and analytes are possible. Therefore, even trace-level analytes can be detected in shorter times with high accuracy. In case of mesoporous sensor materials (pore size > 2 nm), the uptake capacity of small analytes can be higher, and multilayer adsorption is possible. (67) This may reduce the average strength of sensor chromophore-analyte interactions resulting in lower sensitivity or longer response times if compared to dominantly microporous materials. The supporting role of the PTPETCz microporosity is evident from comparative sensing experiments performed using monomer TPETCz-films drop-casted on quartz. These films are strongly emissive but nonporous in nature. As depicted in Figure 3b, a drop-casted TPETCz-film exhibited merely 10% decrease of emission when exposed to 0.2 ppm of TNT (ca. 6 times higher concentration as used for the CMP film) over 2 min, thus corresponding to a (ca. 1 order of magnitude) lower sensitivity compared to PTPETCz. The observed moderate emission quenching in the drop-casted film of monomer TPETCz is expected to be a result of interactions at surface-near centers. Interestingly, PTPETCz films also showed appreciable response to very low TNT concentrations of 10 ppb, as shown in Figure 4a: nearly 30% emission quenching is observed after 2 min of exposure. These results are promising if compared to our previously reported vapor-phase TNT thin-film sensors. (59,60) Excitingly, PTPETCz showed only 20% and 1.4% emission quenching when exposed to high vapor-pressure nitroarenes such as 2,4-dinitrotoluene (DNT, 350 ppb) and 4-nitrotoluene (NT, 64 ppm) for 5 min, respectively. We also performed vapor-phase sensing experiments of PTPETCz with 1,3,5-trinitrobenzene (TNB; 10 ppb) and 1,3-dinitrobenzene (DNB; 47 ppb) at room temperature. On the one hand, no fluorescence quenching of PTPETCz was observed for DNB, while in the presence of TNB fluorescence quenching of only 14% is noticed after 5 min. On the other hand, TNT at room temperature showed a fluorescence quenching of nearly 30% in 2 min. Sensing experiments of TNT in the presence of TNB and DNB were not performed due to the unavailability of safety measures for mixtures of explosives. However, no significant changes in emission are observed when exposed to electron-rich arenes such as chlorobenzene and toluene (Figure 4b). The fluorescence quenching of thin-film sensor when exposed to nitroarene vapors should be affected (1) by molecular interactions between sensor and analyte, (2) by the LUMO/LUMO energy offset, and (3) by the diffusion ability of the analytes into the thin films. The quenching believably occurs due to a photoinduced electron transfer from photoexcited PTPETCz to analyte when the LUMO level of analyte is lower than the LUMO of the polymer. As depicted in Figure S24, the LUMO level of PTPETCz (−3.55 eV) is higher than that of LUMO levels of TNT (−3.93 eV) and TNB (−3.97 eV), comparable to that of 2,4-DNT (−3.41 eV) and 1,3-DNB (−3.59 eV), and lower than that of 4-NT (−3.01 eV). (68) So, an efficient electron transfer from polymer to TNT is possible thus leading to strong fluorescence quenching. The reason for the weak response to other analytes may be related to their different LUMO energy levels that are not sufficiently low for electron transfer. This also implies that a high vapor pressure of the analyte is not significantly enough for quenching. Strikingly, TNB with a similar LUMO level as that of TNT showed only 14% quenching at 25 °C after 5 min, and no further increase in response was observed even after increasing the concentration of TNB (by heating analyte chamber to 50 °C). Unfortunately, we were not able to calculate binding constants for our solid-state measurements. Such selective response to vapor-phase nitroarenes was already reported for small molecule-based carbazole derivatives and linear conjugated polymers. (69−72) To check the effect of film thickness on the sensing performance, experiments were performed with PTPTTCz grown over 20 CV cycles (thickness ca. 61 nm). As seen in Figure 4c, an appreciable fluorescence quenching (46%) was observed when exposed to TNT vapors of 33 ppb for 3 min. This value is relatively lower compared to the 15 nm thick films (95% quenching in 3 min). Possible reasons for this lower response of thicker films may be the higher number of fluorescent receptors and longer analyte diffusion times to reach the fluorescent receptors. So, the thickness of CMP film also significantly affects the sensitivity of the porous polymer toward vapor-phase analytes. The decrease in quenching rate with increasing film thickness was also observed in other reports. (41) When the TNT-exposed films of PTPETCz are washed with a toluene/acetonitrile mixture followed by annealing at 140 °C for 1 h under vacuum, nearly 80% of the emission intensity is recovered, and the films are reusable for further sensing cycles (Figure S26). The sensing response of other two CMP films was also studied. The weakly red emissive PFLCz showed no significant response to TNT vapors when exposed more than 10 min even to higher TNT concentrations (0.2 ppm). This is also evident from photographs of films that are illuminated before and after TNT exposure (Figures S25 & S27). This contrasting behavior can be ascribed to the increased electron-accepting character of the PFLCz-film due to the fluorenone units present in the polymer. Interestingly, polymer PTPEFLCz with both TPE and fluorenone units showed appreciable optical response when exposed to TNT (0.2 ppm). As shown in Figures 4d & S28 the PTPEFLCz emission at 608 nm gradually decreased with time when exposed to TNT vapors (0.2 ppm): nearly 70% emission quenching is observed after 2 min. Photographs of the illuminated films showed a clear decrease in the emission intensity when exposed to TNT vapors.

Figure 3

Figure 3. (a) Gradual decrease of PTPETCz emission when exposed to 33 ppb of TNT vapor over time. (inset) Photographs of illuminated PTPETCz thin films on ITO (i) under UV lamp and (ii), (iii) under laser source before and after exposure to TNT, respectively. (b) Fluorescence quenching of PTPETCz films (blue) with time in the presence of TNT vapor (33 ppb), compared to the fluorescence quenching of a drop-casted monomer film (TPETCz) during exposure to TNT vapor (0.2 ppm). (inset) Photographs of illuminated TPETCz film (iv) before and (v) after TNT exposure.

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Figure 4

Figure 4. (a) Fluorescence quenching of a PTPETCz film with time in the presence of TNT vapor (10 ppb) and (b) degree of emission quenching of PTPETCz films when exposed to various analyte vapors; TNT (33 ppb, 3 min) and TNB (10 ppb), 1,3-DNB (47 ppb), saturated vapors of 2,4-dinitrotoluene (DNT), nitrotoluene (NT), chlorobenzene (ClBen), and toluene (Tol), exposure time 5 min. (c) Change in fluorescence intensity with time in the presence of TNT vapor (33 ppb) for PTPETCz films of ca. 61 nm thickness and (d) change in fluorescence intensity with time in the presence of TNT vapor (0.2 ppm) for PTPEFLCz films.

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4. Conclusions

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In summary, we have generated different CMP thin films containing two types of fluorescent segments using the electrochemical oxidative polymerization method, including a copolymer made from two monomers of different structure. All CMP films are microporous with appreciable BET surface areas of 930–509 m2/g. Two of the CMPs show an intense fluorescence. This unique combination of properties produces a sensitive and selective optical response to trinitrotoluene in the vapor phase by florescence quenching, for TNT concentrations down to 10 ppb. Our study suggests that combination of electron-donating TPE units combined with an intrinsic microporosity in TPE-containing CMPs is a promising approach for the sensing of electron-poor analytes. Vapor-phase sensing using CMP thin films is, therefore, an interesting platform for developing reliable vapor-phase sensors, also toward other relevant explosives as royal demolition explosive (RDX), trinitrophenol, etc. Hereby, the strategy of synthesizing copolymer-based thin films from electronically different monomers can be useful for a fine-tuning of the electronic properties of the resulting CMPs, possibly also for the development of thin-film materials for visible-light photocatalysis or organic optoelectronics.

Supporting Information

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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsanm.8b01779.

  • Synthetic procedure of monomer and bulk polymers, CV of polymers in monomer-free solution, FTIR spectra, solid-state NMR spectra, TGA, absorption and emission spectra of polymer films, ultraviolet photoemission spectra of polymer films, polymer energy-level diagram (PDF)

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Author Information

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  • Corresponding Author
  • Authors
    • André Räupke - Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany
    • Kai Oliver Brinkmann - Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany
    • Thomas Riedl - Institute of Electronic Devices, University of Wuppertal, Rainer-Gruenter-Str. 21, 42119 Wuppertal, Germany
    • Gunther Brunklaus - Institut für Physikalische Chemie, Westfälische Wilhelms-Universität, Corrensstr. 46, D-48149 Münster, Germany;  Orcidhttp://orcid.org/0000-0003-0030-1383
    • Ullrich Scherf - Macromolecular Chemistry Group, Bergische Universität Wuppertal, Gaußstraße 20, 42119 Wuppertal, Germany
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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V.M.S. thanks Alexander von Humboldt foundation for postdoctoral fellowship.

References

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    Cooper, A. I. Conjugated Microporous Polymers. Adv. Mater. 2009, 21, 1291– 1295,  DOI: 10.1002/adma.200801971
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    Conjugated microporous polymers
    Cooper, Andrew I.
    Advanced Materials (Weinheim, Germany) (2009), 21 (12), 1291-1295CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Conjugated microporous polymers are of great interest because they have potential to combine high surface areas in the dry state with phys. properties relevant to org. electronics. A series of recent reports has shown that materials such as poly(aryleneethynylene)s (PAEs), poly(phenylene butadiynylene)s, poly(phenylene vinylene), poly(p-phenylene)s, polysilanes, polyanilines, and polytriazines can be produced as microporous networks with apparent Brunauer-Emmett-Teller surface areas of more than 1000 m2 g-1 in some cases. Micropore size and surface area can be synthetically fine-tuned in amorphous PAE polymers and copolymers, something which was previously thought to be the preserve of ordered cryst. materials such as metal org. frameworks. We review in this Research News article recent progress made by our group and other with particular emphasis on the possible future applications of these materials.
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    Schmidt, J.; Weber, J.; Epping, J. D.; Antonietti, M.; Thomas, A. Microporous Conjugated Poly(thienylenearylene) Networks. Adv. Mater. 2009, 21, 702– 705,  DOI: 10.1002/adma.200802692
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    Suresh, V. M.; Bonakala, S.; Roy, S.; Balasubramanian, S.; Maji, T. K. Synthesis, Characterization, and Modeling of a Functional Conjugated Microporous Polymer: CO2 Storage and Light Harvesting. J. Phys. Chem. C 2014, 118, 24369– 24376,  DOI: 10.1021/jp508734z
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    Synthesis, Characterization, and Modeling of a Functional Conjugated Microporous Polymer: CO2 Storage and Light Harvesting
    Suresh, Venkata M.; Bonakala, Satyanarayana; Roy, Syamantak; Balasubramanian, Sundaram; Maji, Tapas Kumar
    Journal of Physical Chemistry C (2014), 118 (42), 24369-24376CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
    Rationalization of structure and properties of metallic glasses porous solids at the microscopic level is essential in developing advanced materials. We delineate the structural simulation, physicochem., physicochem. of a designed tetraphenylethene-based metallic glasses conjugated microporous polymer TPE-CMP (1) and its gas storage and photophys. properties. The polymer 1 exhibits high sp. surface area of 854 m2/g. 1 showed appreciable CO2 (32.4 wt. %) uptake at 195 K up to 1 atm and 31.6 wt. % at 273 K up to 35 bar. The structural simulation, physicochem. of 1 obtained through computational methods is quant. consistent with exptl. observations. The microporous structural simulation, physicochem. of 1 was further validated by a calcn. of CO2 adsorption isotherm obtained through GCMC simulations. Quantum chem. calcns. were employed to understand the nature of interactions of CO2 with the constituents of the framework 1. π-π interaction with strength of 19 kJ/mol was obsd. between CO2 and the Ph rings of TPE. 1 shows strong turn-on greenish-yellow emission due to the restriction of Ph ring rotation of TPE node. This framework induced emission (FIE) of microporous polymer 1 is further exploited for light-harvesting applications by noncovalent encapsulation of a suitable acceptor dye, rhodamine B (RhB), in the framework.
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    Liao, Y.; Cheng, Z.; Zuo, W.; Thomas, A.; Faul, C. F. J. Nitrogen-Rich Conjugated Microporous Polymers: Facile Synthesis, Efficient Gas Storage, and Heterogeneous Catalysis. ACS Appl. Mater. Interfaces 2017, 9, 38390– 38400,  DOI: 10.1021/acsami.7b09553
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    Nitrogen-Rich Conjugated Microporous Polymers: Facile Synthesis, Efficient Gas Storage, and Heterogeneous Catalysis
    Liao, Yaozu; Cheng, Zhonghua; Zuo, Weiwei; Thomas, Arne; Faul, Charl F. J.
    ACS Applied Materials & Interfaces (2017), 9 (44), 38390-38400CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Nitrogen-rich conjugated microporous polymers (NCMPs) have attracted great attention in recent years owing to their polarity, basicity, and ability to coordinate metal ions. Herein, three NCMPs, structurally close to polyaniline, were facilely synthesized via chem. oxidative polymn. between multiconnected aniline precursors. The NCMPs with high N content (11.84 wt %), intrinsic ultramicroporosity (<1 nm), and moderate surface area (485 m2 g-1) show wide-ranging adsorption functionality, e.g., CO2 uptake (11 wt %) and CO2-selectivity over N2 (360, 1 bar), 1.0 wt % H2 storage, as well as 215 wt % iodine vapor uptake at ambient pressure. Moreover, these NCMPs act as support for palladium catalysts and can maintain >94% activity in Suzuki-Miyaura coupling reactions after six continuous runs.
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    Chang, Z.; Zhang, D.-S.; Chen, Q.; Bu, X.-H. Microporous Organic Polymers for Gas Storage and Separation Applications. Phys. Chem. Chem. Phys. 2013, 15, 5430– 5442,  DOI: 10.1039/c3cp50517k
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    Microporous organic polymers for gas storage and separation applications
    Chang, Ze; Zhang, Da-Shuai; Chen, Qiang; Bu, Xian-He
    Physical Chemistry Chemical Physics (2013), 15 (15), 5430-5442CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    A review. Microporous org. polymers (MOPs), an emerging class of functional porous materials featured with the pure org. component have been widely studied in recent years. These materials have potential uses in areas such as storage, sepn., and catalysis. In this Perspective, we focused on the gas storage and sepn. of MOPs. The targeted design and synthesis of MOPs toward the enhancement of gas capacity and selectivity are discussed. Furthermore, special emphasis is given to the post-synthesis modification of MOPs which have been proved to be effective methods to accurately tune the desired properties.
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    Ben, T.; Pei, C.; Zhang, D.; Xu, J.; Deng, F.; Jing, X.; Qiu, S. Gas Storage in Porous Aromatic Frameworks (PAFs). Energy Environ. Sci. 2011, 4, 3991– 3999,  DOI: 10.1039/c1ee01222c
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    Gas storage in porous aromatic frameworks (PAFs)
    Ben, Teng; Pei, Cuiying; Zhang, Daliang; Xu, Jun; Deng, Feng; Jing, Xiaofei; Qiu, Shilun
    Energy & Environmental Science (2011), 4 (10), 3991-3999CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
    A series of porous arom. frameworks (PAFs) were synthesized via a Yamamoto-type Ullmann reaction contg. quadricovalent Si (PAF-3) and Ge (PAF-4). These PAFs are thermally stable up to 465°C for PAF-3 and 443°C for PAF-4, corresponding to a 5% wt. loss according to the TG pattern. As PAF-1, they exhibit high surface areas (up to 2932 m2 g-1) and excellent adsorption ability to hydrogen, methane, and carbon dioxide. Low pressure gas uptake expts. on PAFs show PAF-3 has the highest heat of adsorption (Qst) of hydrogen (6.6 kJ mol-1) and carbon dioxide (19.2 kJ mol-1), while PAF-4 has the highest Qst for methane adsorption (23.2 kJ mol-1) among PAFs. Gas mol. recognition at 273 K was performed and results show only greenhouse gases such as carbon dioxide and methane could be adsorbed onto PAFs.
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    Rao, K. V.; Haldar, R.; Maji, T. K.; George, S. J. Dynamic, Conjugated Microporous Polymers: Visible Light Harvesting via Guest-Responsive Reversible Swelling. Phys. Chem. Chem. Phys. 2016, 18, 156– 163,  DOI: 10.1039/C5CP05052A
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    Dynamic, conjugated microporous polymers: visible light harvesting via guest-responsive reversible swelling
    Rao K Venkata; Haldar Ritesh; Maji Tapas Kumar; George Subi J
    Physical chemistry chemical physics : PCCP (2016), 18 (1), 156-63 ISSN:.
    The light-harvesting properties of two fluorescent dynamic conjugated microporous organic polymers (Py-PP and Py-BPP) rendered with pyrene chromophores are described. The hydrophobic and dynamic nature of these porous frameworks allows the selective capture of various organic solvents by instantaneous swelling at room temperature. Moreover, the dynamic nature of these frameworks indicates the swelling process with visible volume expansion and enhanced fluorescence. This was further explored for the rapid encapsulation of various fluorescent chromophoric guests at room temperature and investigated for photoinduced energy transfer process. The resultant host-guest antenna materials showed efficient light-harvesting and funnelling of excitation energy of host framework towards the entrapped guest molecule. This process further yielded solid-state luminescent materials with tunable emission. This work holds a great promise on the design of smart porous organic solids from π-conjugated small molecules for optoelectronics, sensing and separation.
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    Suresh, V. M.; Bandyopadhyay, A.; Roy, S.; Pati, S. K.; Maji, T. K. Highly Luminescent Microporous Organic Polymer with Lewis Acidic Boron Sites on the Pore Surface: Ratiometric Sensing and Capture of F(−) Ions. Chem. - Eur. J. 2015, 21, 10799– 10804,  DOI: 10.1002/chem.201500406
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    Highly Luminescent Microporous Organic Polymer with Lewis Acidic Boron Sites on the Pore Surface: Ratiometric Sensing and Capture of F- Ions
    Suresh, Venkata M.; Bandyopadhyay, Arkamita; Roy, Syamantak; Pati, Swapan K.; Maji, Tapas Kumar
    Chemistry - A European Journal (2015), 21 (30), 10799-10804CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Reversible and selective capture/detection of F- ions in water is of the utmost importance, as excess intake leads to adverse effects on human health. Highly robust Lewis acidic luminescent porous org. materials have potential for efficient sequestration and detection of F- ions. Herein, the rational design and synthesis of a boron-based, Lewis acidic microporous org. polymer (BMOP) derived from tris(4-bromo-2,3,5,6-tetramethylphenyl)boron nodes and diethynylbiphenyl linkers with a pore size of 1.08 nm for selective turn-on sensing and capture of F- ion are reported. The presence of a vacant pπ orbital on the boron center of BMOP results in intramol. charge transfer (ICT) from the linker to boron. BMOP shows selective turn-on blue emission for F- ions in aq. mixts. with a detection limit of 2.6 μΜ. Strong B-F interactions facilitate rapid sequestration of F- by BMOP. The ICT emission of BMOP can be reversibly regenerated by addn. of an excess of water, and the polymer can be reused several times.
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    Chen, L.; Honsho, Y.; Seki, S.; Jiang, D. Light-Harvesting Conjugated Microporous Polymers: Rapid and Highly Efficient Flow of Light Energy with a Porous Polyphenylene Framework as Antenna. J. Am. Chem. Soc. 2010, 132, 6742– 6748,  DOI: 10.1021/ja100327h
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    Light-harvesting conjugated microporous polymers: rapid and highly efficient flow of light energy with a porous polyphenylene framework as antenna
    Chen, Long; Honsho, Yoshihito; Seki, Shu; Jiang, Donglin
    Journal of the American Chemical Society (2010), 132 (19), 6742-6748CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The mol. design of light-harvesting antennae requires not only the segregation of a large no. of chromophore units in a confined nanospace but also the cooperation of these units in achieving highly efficient energy transduction. This article describes the synthesis and functions of a polyphenylene-based conjugated microporous polymer (PP-CMP). PP-CMP was recently designed and synthesized by Suzuki polycondensation reaction and used as an antenna for the noncovalent construction of a light-harvesting system. In contrast to linear polyphenylene, PP-CMP consists of conjugated three-dimensional polyphenylene scaffolds and holds inherent porous structure with uniform pore size (1.56 nm) and large surface area (1083 m2 g-1). It emits blue photoluminescence, is capable of excitation energy migration over the framework, and enables rapid transportation of charge carrier with intrinsic mobility as high as 0.04 cm2 V-1 s-1. The microporous structure of PP-CMP allows for the spatial confinement of energy-accepting coumarin 6 mols. in the pores and makes the high-throughput synthesis of light-harvesting systems with designable donor-acceptor compns. possible. Excitation of the PP-CMP skeleton leads to brilliant green emission from coumarin 6, with an intensity 21-fold as high as that upon direct excitation of coumarin 6 itself, while the fluorescence from PP-CMP itself is wholly quenched as a result of energy transfer from the light-harvesting PP-CMP framework to coumarin 6. The PP-CMP skeleton is highly cooperative, with an av. of 176 phenylene units working together to channel the excitation energy to one coumarin 6 mol., and features the energy-transfer process with quick, efficient, and vectorial character. These unique characteristics clearly originate from the conjugated porous structure and demonstrate the usefulness of CMPs in the exploration of π-electronic functions, in addn. to their gas adsorption properties thus far reported.
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    Zhao, Y.-C.; Zhou, D.; Chen, Q.; Zhang, X.-J.; Bian, N.; Qi, A.-D.; Han, B.-H. Thionyl Chloride-Catalyzed Preparation of Microporous Organic Polymers through Aldol Condensation. Macromolecules 2011, 44, 6382– 6388,  DOI: 10.1021/ma201264w
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    Thionyl Chloride-Catalyzed Preparation of Microporous Organic Polymers through Aldol Condensation
    Zhao, Yan-Chao; Zhou, Ding; Chen, Qi; Zhang, Xin-Jian; Bian, Ning; Qi, Ai-Di; Han, Bao-Hang
    Macromolecules (Washington, DC, United States) (2011), 44 (16), 6382-6388CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    We demonstrated the synthesis of five kinds of microporous org. polymers based on aldol self-condensation of di- and multiacetyl-contg. building blocks catalyzed by thionyl chloride. The α,β-unsatd. ketone (dimerization) and 1,3,5-trisubstituted benzene (cyclotrimerization) can be obsd. in the resulting polymers by Fourier transform IR and solid-state 13C CP/MAS NMR spectroscopy. The regular spheres and nanometer-scaled cavities were also seen from SEM and high-resoln. transmission electron microscopy images. The highest Brunauer-Emmet-Teller sp. surface area up to 832 m2 g-1 was obtained for the resulting polymers with a pore vol. of 0.48 cm3 g-1. The polymers show great hydrogen storage capacities (up to 1.56 wt %) at 77 K and 1 bar. These excellent characteristics would make them become promising candidates for heterogeneous catalysis, sepn., and gas storage.
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    Ben, T.; Ren, H.; Ma, S.; Cao, D.; Lan, J.; Jing, X.; Wang, W.; Xu, J.; Deng, F.; Simmons, J. M.; Qiu, S.; Zhu, G. Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area. Angew. Chem., Int. Ed. 2009, 48, 9457– 9460,  DOI: 10.1002/anie.200904637
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    Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area
    Ben, Teng; Ren, Hao; Ma, Shengqian; Cao, Dapeng; Lan, Jianhui; Jing, Xiaofei; Wang, Wenchuan; Xu, Jun; Deng, Feng; Simmons, Jason M.; Qiu, Shilun; Zhu, Guangshan
    Angewandte Chemie, International Edition (2009), 48 (50), 9457-9460, S9457/1-S9457/16CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    With the assistance of computational design, a porous arom. framework with an unprecedented high surface area of 7100 m2g-1 has been successfully synthesized. PAF-1 possesses local diamond-like tetrahedral bonding of tetraphenylenemethane building units to produce exceptional thermal and hydrothermal stabilities. In addn., PAF-I demonstrates high uptake capacities of hydrogen and carbon dioxide, as well as benzene and toluene vapors. The strategy presented in this work opens a new avenue for the design and construction of highly porous materials with exceptional stabilities for clean energy and environmental applications.
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    Zhi, Y.; Li, K.; Xia, H.; Xue, M.; Mu, Y.; Liu, X. Robust Porous Organic Polymers as Efficient Heterogeneous Organo-Photocatalysts for Aerobic Oxidation Reactions. J. Mater. Chem. A 2017, 5, 8697– 8704,  DOI: 10.1039/C7TA02205K
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    Robust porous organic polymers as efficient heterogeneous organo-photocatalysts for aerobic oxidation reactions
    Zhi, Yongfeng; Li, Kun; Xia, Hong; Xue, Ming; Mu, Ying; Liu, Xiaoming
    Journal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (18), 8697-8704CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
    Metal-free, visible-light active and heterogeneous org. photocatalysts offer a more sustainable and environmentally friendly alternative to traditional metal-based catalysts. Here a porous org. hyper-crosslinked polymer, CF-HCP, was successfully synthesized through a facile and cost-effective process. The chem. and structural properties of CF-HCP were fully characterized by using powder X-ray diffraction anal., Fourier transform IR spectroscopy, 13C solid-state NMR spectroscopy, electron microscopy, thermogravimetric anal., XPS and nitrogen adsorption. The new three-dimensional hyper-crosslinked network possesses a high Brunauer-Emmett-Teller (BET) sp. surface area up to 1200 m2 g-1 with a pore vol. of 0.92 cm3 g-1, and exhibits good thermal, chem. and photochem. stability. Importantly, CF-HCP was found to be a highly effective heterogeneous photocatalyst for a wide range of org. reactions, including the oxidative coupling of primary amines, dehydrogenation of nonactive secondary amine substrates, and selective oxidn. of sulfide under visible-light irradn. and using mol. oxygen as a clean oxidant. In particular, mild reaction conditions, ease of product sepn. by simple filtration, significant recyclability and low cost make this network material an economical and eco-friendly catalyst for the prepn. of versatile org. compds.
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    Qiao, S.; Wang, T.; Huang, W.; Jiang, J.-X.; Du, Z.; Shieh, F.-K.; Yang, R. Dendrimer-Like Conjugated Microporous Polymers. Polym. Chem. 2016, 7, 1281– 1289,  DOI: 10.1039/C5PY01767J
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    Dendrimer-like conjugated microporous polymers
    Qiao, Shanlin; Wang, Ting; Huang, Wei; Jiang, Jia-Xing; Du, Zhengkun; Shieh, Fa-Kuen; Yang, Renqiang
    Polymer Chemistry (2016), 7 (6), 1281-1289CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
    Four dendrimer-like polycarbazole conjugated polymer networks P-G1-T, P-G2-T, P-G1-Fo and P-G2-Fo were designed and synthesized by FeCl3 oxidative coupling polymn. Arom. thiophene and fluorenone units were employed as the linkers between carbazole units to construct the building blocks. The first generation polymers (1st) were produced from the monomers contg. two carbazole units, while the second generation polymers (2nd) were produced from the monomers with six carbazole units, which feature double oxidative polymn. sites compared with the monomers for the 1st generation. It was found that the 2nd generation polymers show a higher Brunauer-Emmett-Teller (BET) surface area and a higher gas adsorption performance than the 1st generation polymers because of more reactive sites and larger torsion angles in the monomers for the 2nd generation, which led to a highly crosslinked polymer structure and thus a high surface area. All of the polymers show high isosteric heats of CO2 adsorption over 33 kJ mol-1 because the incorporation of heteroatoms (N, S and/or O) into the skeleton of the polymers enhanced the interaction between the pore wall and CO2 mols.
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    Chen, Q.; Liu, D.-P.; Luo, M.; Feng, L.-J.; Zhao, Y.-C.; Han, B.-H. Nitrogen-Containing Microporous Conjugated Polymers Via Carbazole-Based Oxidative Coupling Polymerization: Preparation, Porosity, and Gas Uptake. Small 2014, 10, 308– 315,  DOI: 10.1002/smll.201301618
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    Nitrogen-Containing Microporous Conjugated Polymers via Carbazole-Based Oxidative Coupling Polymerization: Preparation, Porosity, and Gas Uptake
    Chen, Qi; Liu, De-Peng; Luo, Min; Feng, Li-Juan; Zhao, Yan-Chao; Han, Bao-Hang
    Small (2014), 10 (2), 308-315CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Facile prepn. of microporous conjugated polycarbazoles via carbazole-based oxidative coupling polymn. is reported. The process to form the polymer network has cost-effective advantages such as using a cheap catalyst, mild reaction conditions, and requiring a single monomer. Because no other functional groups such as halo groups, boric acid, and alkyne are required for coupling polymn., properties derived from monomers are likely to be fully retained and structures of final polymers are easier to characterize. A series of microporous conjugated polycarbazoles (CPOP-2-7) with permanent porosity are synthesized using versatile carbazolyl-bearing 2D and 3D conjugated core structures with non-planar rigid conformation as building units. The Brunauer-Emmett-Teller sp. surface area values for these porous materials vary between 510 and 1430 M2 g-1. The dominant pore sizes of the polymers based on the different building blocks are located between 0.59 and 0.66 nm. Gas (H2 and CO2) adsorption isotherms show that CPOP-7 exhibits the best uptake capacity for hydrogen (1.51% at 1.0 bar and 77 K) and carbon dioxide (13.2% at 1.0 bar and 273 K) among the obtained polymers. Furthermore, its high CH4/N2 and CO2/N2 adsorption selectivity gives polymer CPOP-7 potential application in gas sepn.
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    Bandyopadhyay, S.; Pallavi, P.; Anil, A. G.; Patra, A. Fabrication of Porous Organic Polymers in the Form of Powder, Soluble in Organic Solvents and Nanoparticles: A Unique Platform for Gas Adsorption and Efficient Chemosensing. Polym. Chem. 2015, 6, 3775– 3780,  DOI: 10.1039/C5PY00235D
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    Fabrication of porous organic polymers in the form of powder, soluble in organic solvents and nanoparticles: a unique platform for gas adsorption and efficient chemosensing
    Bandyopadhyay, Sujoy; Pallavi, Pragyan; Anil, Amith G.; Patra, Abhijit
    Polymer Chemistry (2015), 6 (20), 3775-3780CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
    Conjugated porous org. polymers based on a novel core of tetraphenyl-5,5-dioctylcyclopentadiene (TPDC) have been fabricated in the form of powder (P1), sol. in common org. solvents (P2) as well as aq. dispersion of nanoparticles (P3). Fine tuning of the conditions of polycondensation reactions involving tetrakis(4-bromophenyl)-5,5-dioctylcyclopentadiene and diethynylbenzene leads to the formation of TPDC based polymers in three different forms. P1, P2 and P3 possess high thermal stability (up to 375°C) and are porous in nature. The Brunauer-Emmett-Teller (BET) surface area and total pore vol. of P1 were estd. to be 405 m2 g-1 and 0.68 cm3 g-1 resp. Solid P1 was explored for hydrogen and carbon dioxide adsorption. Soln. of P2 and aq. dispersion of P3 exhibit strong cyan fluorescence and are applied for the sensing of nitroaroms. Steady state and time resolved fluorescence measurements reveal the underlying photophysics of amplified fluorescence quenching of P2 and P3 by nitroaroms. Porosity, gas adsorption, as well as soly., strong fluorescence and sensing capabilities establish TPDC based porous polymers as new multifunctional materials and can find broad applications in sensing and optical devices.
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    Li, Z.; Li, H.; Xia, H.; Ding, X.; Luo, X.; Liu, X.; Mu, Y. Triarylboron-Linked Conjugated Microporous Polymers: Sensing and Removal of Fluoride Ions. Chem. - Eur. J. 2015, 21, 17355– 17362,  DOI: 10.1002/chem.201502241
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    Triarylboron-Linked Conjugated Microporous Polymers: Sensing and Removal of Fluoride Ions
    Li, Zhongping; Li, He; Xia, Hong; Ding, Xuesong; Luo, Xiaolong; Liu, Xiaoming; Mu, Ying
    Chemistry - A European Journal (2015), 21 (48), 17355-17362CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A luminescent conjugated microporous polymer (BCMP-3) has been synthesized in high yield by a carbon-carbon coupling reaction using triarylboron as a building unit. BCMP-3 was fully characterized by using powder x-ray diffraction anal., Fourier transform IR spectroscopy, 13C solid-state NMR spectroscopy, field emission SEM, thermogravimetric anal., and nitrogen and carbon dioxide adsorption. The new three-dimensional conjugated framework possess a high Brunauer-Emmett-Teller (BET) sp. surface area up to 950 M2 g-1 with a pore vol. of 0.768 Cm3 g-1, good stability, and abundant boron sites in the skeleton. Under excited-light irradn., BCMP-3 exhibits strong fluorescent emission at 488 nm with a high abs. quantum yield of 18 % in the solid state. Polymer BCMP-3 acts as a colorimetric and fluorescent chemosensor with high sensitivity and selectivity for F- over other common anions. In addn., the polymer also works as an adsorbent for F- removal and shows good adsorption capacities of up to 24 mg g-1 at equil. F- concns. of 16 mg L-1 and a temp. of 298 K. The adsorption kinetics and isotherm were analyzed by fitting exptl. data with pseudo-second-order kinetics and Langmuir equations. Furthermore, we highlight that BCMP-3 is an adsorbent for fluoride removal that can be efficiently reused many times without loss of adsorption efficiency.
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    Xiang, L.; Zhu, Y.; Gu, S.; Chen, D.; Fu, X.; Zhang, Y.; Yu, G.; Pan, C.; Hu, Y. A Luminescent Hypercrosslinked Conjugated Microporous Polymer for Efficient Removal and Detection of Mercury Ions. Macromol. Rapid Commun. 2015, 36, 1566– 1571,  DOI: 10.1002/marc.201500159
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    A Luminescent Hypercrosslinked Conjugated Microporous Polymer for Efficient Removal and Detection of Mercury Ions
    Xiang, Lu; Zhu, Yunlong; Gu, Shuai; Chen, Dongyang; Fu, Xian; Zhang, Yindong; Yu, Guipeng; Pan, Chunyue; Hu, Yuehua
    Macromolecular Rapid Communications (2015), 36 (17), 1566-1571CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A hypercrosslinked conjugated microporous polymer (HCMP-1) with a robustly efficient absorption and highly specific sensitivity to mercury ions (Hg2+) is synthesized in a one-step Friedel-Crafts alkylation of cost-effective 2,4,6-trichloro-1,3,5-triazine and dibenzofuran in 1,2-dichloroethane. HCMP-1 has a moderate Brunauer-Emmett-Teller sp. surface (432 m2 g-1), but it displays a high adsorption affinity (604 mg g-1) and excellent trace efficiency for Hg2+. The π-π* electronic transition among the arom. heterocyclic rings endows HCMP-1 a strong fluorescent property and the fluorescence is obviously weakened after Hg2+ uptake, which makes the hypercrosslinked conjugated microporous polymer a promising fluorescent probe for Hg2+ detection, owning a super-high sensitivity (detection limit 5 × 10-8 mol L-1).
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    Liu, J.; Yee, K.-K.; Lo, K. K.-W.; Zhang, K. Y.; To, W.-P.; Che, C.-M.; Xu, Z. Selective Ag(I) Binding, H2S Sensing, and White-Light Emission from an Easy-To-Make Porous Conjugated Polymer. J. Am. Chem. Soc. 2014, 136, 2818– 2824,  DOI: 10.1021/ja411067a
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    Selective Ag(I) Binding, H2S Sensing, and White-Light Emission from an Easy-to-Make Porous Conjugated Polymer
    Liu, Jie; Yee, Ka-Kit; Lo, Kenneth Kam-Wing; Zhang, Kenneth Yin; To, Wai-Pong; Che, Chi-Ming; Xu, Zhengtao
    Journal of the American Chemical Society (2014), 136 (7), 2818-2824CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Sepg. silver (Ag+) from lead (Pb2+) is one of the many merits of the porous polymer framework reported here. The selective metal binding stems from the well-defined chelating unit of N-heterocycles, which consists of a triazine (C3N3) ring bonded to three 3,5-dimethylpyrazole moieties. Such a rigid and open triad also serves as the distinct building unit in the fully conjugated 3D polymer scaffold. Because of its strong fluorescence and porosity (e.g., BET surface area: 355 m2/g), and because of the various types of metal species that can be readily taken up, this versatile framework is esp. fit for functionalization. For example, with AgNO3 loaded, the framework solid exhibits a brown color in response to water solns. of H2S, even at the diln. of 5.0 μM (0.17 ppm); whereas cysteine and other biol. relevant thiols do not cause notable change in color. In another example, tunable white-light emission was produced when an Ir(III) complex was doped (e.g., about 0.02% of the polymer wt.) onto the framework. Mechanistically, the bound Ir(III) centers become highly emissive in the orange-red region, complementing the broad, bluish emission from the polymer host to result in the overall white-light quality: the color attributes of the emission are therefore easily tunable by the Ir(III) dopant concn. With this exemplary study, we intend to highlight metal uptake as an effective approach to modify and enrich the properties of porous polymer frameworks and to stimulate interest in further examg. metal-polymer interactions in the context of sensing, sepn., catalyzes, and other applications.
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    Gopalakrishnan, D.; Dichtel, W. R. Direct Detection of RDX Vapor Using a Conjugated Polymer Network. J. Am. Chem. Soc. 2013, 135, 8357– 8362,  DOI: 10.1021/ja402668e
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    Direct Detection of RDX Vapor Using a Conjugated Polymer Network
    Gopalakrishnan, Deepti; Dichtel, William R.
    Journal of the American Chemical Society (2013), 135 (22), 8357-8362CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcn. strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 103 less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here the authors report a crosslinked phenylene vinylene polymer network whose fluorescence is quenched by trace amts. of RDX introduced from soln. or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from soln. or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in crosslinked polymers and framework materials for sensing applications.
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    Liu, X.; Xu, Y.; Jiang, D. Conjugated Microporous Polymers as Molecular Sensing Devices: Microporous Architecture Enables Rapid Response and Enhances Sensitivity in Fluorescence-On and Fluorescence-Off Sensing. J. Am. Chem. Soc. 2012, 134, 8738– 8741,  DOI: 10.1021/ja303448r
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    Conjugated Microporous Polymers as Molecular Sensing Devices: Microporous Architecture Enables Rapid Response and Enhances Sensitivity in Fluorescence-On and Fluorescence-Off Sensing
    Liu, Xiaoming; Xu, Yanhong; Jiang, Donglin
    Journal of the American Chemical Society (2012), 134 (21), 8738-8741CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    Conjugated polymers are attractive materials for the detection of chems. because of their remarkable π-conjugation and photoluminescence properties. The authors report a new strategy for the construction of mol. detection systems with conjugated microporous polymers (CMPs). The condensation of a carbazole deriv., TCB, gives a conjugated microporous polymer (TCB-CMP) that exhibits blue luminescence and possesses a large surface area. Compared with a linear polymer analog, TCB-CMP showed enhanced detection sensitivity and allowed for the rapid detection of arenes upon exposure to their vapors. TCB-CMP displayed prominent fluorescence enhancement in the presence of electron-rich arene vapors and drastic fluorescence quenching in the presence of electron-deficient arene vapors, and it could be reused without a loss of sensitivity and responsiveness. These characteristics are attributed to the microporous conjugated network of the material. Specifically, the micropores absorb arene mols. into the confined space of the polymer, the skeleton possesses a large surface area and provides a broad interface for arenes, and the network architecture facilitates exciton migration over the framework. These structural features function cooperatively, enhancing the signaling activity of TCB-CMP in fluorescence-on and fluorescence-off detection.
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    Patra, A.; Scherf, U. Fluorescent Microporous Organic Polymers: Potential Testbed for Optical Applications. Chem. - Eur. J. 2012, 18, 10074– 10080,  DOI: 10.1002/chem.201200804
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    Fluorescent Microporous Organic Polymers: Potential Testbed for Optical Applications
    Patra, Abhijit; Scherf, Ullrich
    Chemistry - A European Journal (2012), 18 (33), 10074-10080CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Fluorescent microporous org. polymers (MOPs) are an emerging class of porous org. materials with considerable technol. relevance due to great promise in a range of applications. In this respect, innovative optical materials have been developed based on MOPs. In this article, a brief appraisal of the fabrication methodologies of fluorescent MOPs, their optical attributes, and promising application potentials are presented.
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    Wang, D.; Sun, R.; Feng, S.; Li, W.; Liu, H. Retrieving the Original Appearance of Polyhedral Oligomeric Silsesquioxane-Based Porous Polymers. Polymer 2017, 130, 218– 229,  DOI: 10.1016/j.polymer.2017.10.021
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    Retrieving the original appearance of polyhedral oligomeric silsesquioxane-based porous polymers
    Wang, Dengxu; Sun, Ruixue; Feng, Shengyu; Li, Wensi; Liu, Hongzhi
    Polymer (2017), 130 (), 218-229CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
    A class of polyhedral oligomeric silsesquioxane (POSS)-based porous polymers contg. typical π-conjugated units, including biphenyl, tetrahedral silicon-centered units and tetraphenylethene, have been prepd. by Heck reactions of octavinylsilsesquioxane (OVS) with the corresponding brominated monomers. Two sets of reaction conditions were employed to retrieve their original appearance. These materials exhibit tunable appearance with the colors from dark colors to various colors and the phys. forms from coarse powders with irregular shape particles to fine powders with relatively uniform solid spheres by altering the reaction conditions from method A to method B. It is found that the variation of appearance leads to the alteration of the fluorescence from nearly no fluorescence to bright fluorescence. Considering the conjugated feature of these polymers, we speculate that these polymers were afforded as their original appearance by method B. This finding could explain the unexpected phenomenon that many conjugated porous polymers exhibit no or very low fluorescence despite of their π-conjugated structures, i.e., their real appearance may be covered by the residuals in the networks. Thus, researchers should deliberately consider the material's appearance when prepg. fluorescent porous polymers. Addnl., samples with fine powders show excellent dispersion stability in solvents, which is beneficial for the use of these materials in soln. processable methodologies such as spin-coating. Furthermore, these materials show efficient fluorescence quenching for nitrobenzene vapor in thin films, thereby indicating their potential application as sensing agents for the detection of explosives.
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    Ko, J. H.; Moon, J. H.; Kang, N.; Park, J. H.; Shin, H.-W.; Park, N.; Kang, S.; Lee, S. M.; Kim, H. J.; Ahn, T. K.; Lee, J. Y.; Son, S. U. Engineering of Sn-Porphyrin Networks on the Silica Surface: Sensing of Nitrophenols in Water. Chem. Commun. (Cambridge, U. K.) 2015, 51, 8781– 8784,  DOI: 10.1039/C5CC02144H
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    Engineering of Sn-porphyrin networks on the silica surface: sensing of nitrophenols in water
    Ko, Ju Hong; Moon, Jong Hun; Kang, Narae; Park, Joon Hyun; Shin, Hee-Won; Park, Nojin; Kang, Sungah; Lee, Sang Moon; Kim, Hae Jin; Ahn, Tae Kyu; Lee, Jin Yong; Son, Seung Uk
    Chemical Communications (Cambridge, United Kingdom) (2015), 51 (42), 8781-8784CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Sn-porphyrin networks were engineered on the surface of a thin layer chromatog. (TLC) plate via Sonogashira coupling of the Sn-porphyrin building block and 1,4-diiodobenzene. The Sn-porphyrin film showed a strong Soret band absorption at 422 nm, emission at 600-630 nm, and excellent sensing performance toward nitrophenols in water.
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    Sun, R.; Huo, X.; Lu, H.; Feng, S.; Wang, D.; Liu, H. Recyclable Fluorescent Paper Sensor for Visual Detection of Nitroaromatic Explosives. Sens. Actuators, B 2018, 265, 476– 487,  DOI: 10.1016/j.snb.2018.03.072
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    Recyclable fluorescent paper sensor for visual detection of nitroaromatic explosives
    Sun, Ruixue; Huo, Xiaojuan; Lu, Hang; Feng, Shengyu; Wang, Dengxu; Liu, Hongzhi
    Sensors and Actuators, B: Chemical (2018), 265 (), 476-487CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
    Development of rapid, sensitive, and visual detection of nitroarom. explosives is of great importance for homeland security and human safety. Herein, three novel fluorescent nanoporous polymers (FNPs), HPP-1-HPP-3, were first prepd. by Heck reactions of octavinylsilsesquioxane with ethene derivs. contg. bis-, tri-, or tetrakis- bromophenyl groups. Based on highly sensitive detection of explosives, including p-nitrotoluene (NT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), 4-nitrophenol (NP), 2,4-dinitrophenol (DNP) and picric acid (PA), and high selectivity for detecting TNT and PA, by HPP-2 dispersion in ethanol, a fluorescent paper sensor was developed by a new fabrication process, i.e., vacuum filtrating of HPP-2 dispersion in ethanol, followed by washing and natural drying. The resultant paper sensor was found to be sensitive to explosives in the soln., solid and vapor phase with a rapid response time of < 10 s by visually observing the fluorescence quenching phenomenon. Moreover, this paper sensor is recyclable with desirable fluorescence resuming ratio, which is higher than 75% after 10 times recycle detection. This developed paper sensor is promisingly applied for rapid, on-site and visual sensing of explosive residuals. The remarkable fluorescence and reusability of this sensor could be expanded to other fluorescence detection of residuals.
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    Palma-Cando, A.; Preis, E.; Scherf, U. Silicon- or Carbon-Cored Multifunctional Carbazolyl Monomers for the Electrochemical Generation of Microporous Polymer Films. Macromolecules 2016, 49, 8041– 8047,  DOI: 10.1021/acs.macromol.6b02025
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    Gu, C.; Huang, N.; Wu, Y.; Xu, H.; Jiang, D. Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity. Angew. Chem., Int. Ed. 2015, 54, 11540– 11544,  DOI: 10.1002/anie.201504786
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    Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity
    Gu, Cheng; Huang, Ning; Wu, Yang; Xu, Hong; Jiang, Donglin
    Angewandte Chemie, International Edition (2015), 54 (39), 11540-11544CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Porous org. polymers allow the integration of various π-units into robust porous π-networks, but they are usually synthesized as unprocessable solids with poor light-emitting performance as a result of aggregation-related excitation dissipation. Herein, we report a general strategy for the synthesis of highly emissive photofunctional porous polymer films on the basis of a complementary scheme for the structural design of aggregation-induced-emissive π-systems. We developed a high-throughput and facile method for the direct synthesis of large-area porous thin films at the liq.-electrode interface. The approach enables the prepn. of microporous films within only a few seconds or minutes and allows precise control over their thickness with sub-nanometer precision. By virtue of rapid photoinduced electron transfer, the thin films can detect explosives with enhanced sensitivity to low parts-per-million levels in a selective manner.
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    Palma-Cando, A.; Brunklaus, G.; Scherf, U. Thiophene-Based Microporous Polymer Networks via Chemical or Electrochemical Oxidative Coupling. Macromolecules 2015, 48, 6816– 6824,  DOI: 10.1021/acs.macromol.5b01821
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    Thiophene-Based Microporous Polymer Networks via Chemical or Electrochemical Oxidative Coupling
    Palma-Cando, Alex; Brunklaus, Gunther; Scherf, Ullrich
    Macromolecules (Washington, DC, United States) (2015), 48 (19), 6816-6824CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Four thiophene-based monomers were synthesized by Stille- or Suzuki-type couplings followed by chem. or electrochem. polymn. into microporous polymer networks (MPNs) with high BET surface areas (SBET). Similar SBET values of up to 2020 and 2135 m2 g-1 were detd. for tetraphenylmethane-cored bulk MPN powders and thin films, resp. Electrochem. polymn. in boron trifluoride di-Et etherate (BFEE)/dichloromethane (DCM) mixts. allows for the generation of MPN films with optimized porosity. Moreover, an interesting effect of boron trifluoride on the connectivity of the monomeric units during electropolymn. is obsd. for 3-thienyl-based monomers. Finally, the electrochem. redn. of 1,3,5-trinitrobenzene at MPN-modified glassy carbon (GC) electrodes shows increased cathodic responses compared to non-modified GC electrodes due to interaction between electron-deficient nitroarom. analyte and electron-rich MPN film. The influence of the sp. surface area of MPNs on the electrochem. response is also studied for this class of materials.
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    Zhang, H.; Zhang, Y.; Gu, C.; Ma, Y. Electropolymerized Conjugated Microporous Poly(zinc-porphyrin) Films as Potential Electrode Materials in Supercapacitors. Adv. Energy Mater. 2015, 5, 1402175,  DOI: 10.1002/aenm.201402175
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    Carbas, B. B.; Odabas, S.; Türksoy, F.; Tanyeli, C. Synthesıs of a New Electrochromıc Polymer Based on Tetraphenylethylene Cored Tetrakıs Carbazole Complex and its Electrochromıc Devıce Application. Electrochim. Acta 2016, 193, 72– 79,  DOI: 10.1016/j.electacta.2016.02.024
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    Gu, C.; Huang, N.; Chen, Y.; Zhang, H.; Zhang, S.; Li, F.; Ma, Y.; Jiang, D. Porous Organic Polymer Films with Tunable Work Functions and Selective Hole and Electron Flows for Energy Conversions. Angew. Chem., Int. Ed. 2016, 55, 3049– 3053,  DOI: 10.1002/anie.201510723
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    Porous Organic Polymers Films with Tunable Work Functions and Selective Hole and Electron Flows for Energy Conversions
    Gu, Cheng; Huang, Ning; Chen, Youchun; Zhang, Huanhuan; Zhang, Shitong; Li, Fenghong; Ma, Yuguang; Jiang, Donglin
    Angewandte Chemie, International Edition (2016), 55 (9), 3049-3053CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Org. optoelectronics are promising technologies for energy conversion. However, the electrode interlayer, a key material between active layers and conducting electrodes that controls the transport of charge carriers in and out of devices, is still a chem. challenge. Herein, we report a class of porous org. polymers with tunable work function as hole- and electron-selective electrode interlayers. The network with organoborane and carbazole units exhibits extremely low work-function-selective electron flow, while upon ionic ligation and electro-oxidn., the network significantly increases the work function and turns into hole conduction. We demonstrate their outstanding functions as anode and cathode interlayers in energy-converting solar cells and light-emitting diodes.
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    Gu, C.; Huang, N.; Chen, Y.; Qin, L.; Xu, H.; Zhang, S.; Li, F.; Ma, Y.; Jiang, D. π-Conjugated Microporous Polymer Films: Designed Synthesis, Conducting Properties, and Photoenergy Conversions. Angew. Chem., Int. Ed. 2015, 54, 13594– 13598,  DOI: 10.1002/anie.201506570
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    π-Conjugated Microporous Polymer Films: Designed Synthesis, Conducting Properties, and Photoenergy Conversions
    Gu, Cheng; Huang, Ning; Chen, Youchun; Qin, Leiqiang; Xu, Hong; Zhang, Shitong; Li, Fenghong; Ma, Yuguang; Jiang, Donglin
    Angewandte Chemie, International Edition (2015), 54 (46), 13594-13598CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Conjugated microporous polymers are a unique class of polymers that combine extended π-conjugation with inherent porosity. However, these polymers are synthesized through soln.-phase reactions to yield insol. and unprocessable solids, which preclude not only the evaluation of their conducting properties but also the fabrication of thin films for device implementation. Here, we report a strategy for the synthesis of thin films of π-conjugated microporous polymers by designing thiophene-based electropolymn. at the soln.-electrode interface. High-quality films are prepd. on a large area of various electrodes, the film thickness is controllable, and the films are used for device fabrication. These films are outstanding hole conductors and, upon incorporation of fullerenes into the pores, function as highly efficient photoactive layers for energy conversions. Our film strategy may boost the applications in photocatalysis, energy storage, and optoelectronics.
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    Gu, C.; Chen, Y.; Zhang, Z.; Xue, S.; Sun, S.; Zhang, K.; Zhong, C.; Zhang, H.; Pan, Y.; Lv, Y.; Yang, Y.; Li, F.; Zhang, S.; Huang, F.; Ma, Y. Electrochemical Route to Fabricate Film-Like Conjugated Microporous Polymers and Application for Organic Electronics. Adv. Mater. 2013, 25, 3443– 3448,  DOI: 10.1002/adma.201300839
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    Electrochemical Route to Fabricate Film-Like Conjugated Microporous Polymers (CMPs) and Application for Organic Electronics
    Gu, Cheng; Chen, Youchun; Zhang, Zhongbo; Xue, Shanfeng; Sun, Shuheng; Zhang, Kai; Zhong, Chengmei; Zhang, Huanhuan; Pan, Yuyu; Lv, Ying; Yang, Yanqin; Li, Fenghong; Zhang, Suobo; Huang, Fei; Ma, Yuguang
    Advanced Materials (Weinheim, Germany) (2013), 25 (25), 3443-3448CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Authors report a novel strategy to fabricate CMP films electrochem., and highlight the application of CMP films in electronic devices. Electropolymn. (EP) with concurrent polymer film deposition has proven to be an expecially useful method to process cross-linked polymer network films. The authors intentionally synthesized the EP precursor TPTCz, which combines a tetrahedral tetraphenylmethane core and four peripheral carbazole groups.
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    Palma-Cando, A.; Scherf, U. Electrochemically Generated Thin Films of Microporous Polymer Networks: Synthesis, Properties, and Applications. Macromol. Chem. Phys. 2016, 217, 827– 841,  DOI: 10.1002/macp.201500484
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    Electrochemically Generated Thin Films of Microporous Polymer Networks: Synthesis, Properties, and Applications
    Palma-Cando, Alex; Scherf, Ullrich
    Macromolecular Chemistry and Physics (2016), 217 (7), 827-841CODEN: MCHPES; ISSN:1022-1352. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A review. Electrochem. oxidative polymn. of rigid, multifunctional monomers allows for the synthesis of microporous thin films with high surface areas. Multifunctional, carbazole- and thiophene-based rigid monomers were utilized as rigid 3D building blocks (tectons) toward microporous polymer films with relatively smooth surface morphol. Within the last four years, several studies following this approach were published that report interesting results on the application of these electrogenerated films in org. electronics, photoluminescence-based or electrochem. chemodetectors, electrochem. supercapacitors, and light-harvesting antennae for exciton pumping. In this work, the synthetic approaches for the electrochem. polymn. of multifunctional carbazole- and thiophene-based tectons and resulting properties and application possibilities of the electrogenerated microporous polymer films are reviewed.
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    Palma-Cando, A.; Scherf, U. Electrogenerated Thin Films of Microporous Polymer Networks with Remarkably Increased Electrochemical Response to Nitroaromatic Analytes. ACS Appl. Mater. Interfaces 2015, 7, 11127– 11133,  DOI: 10.1021/acsami.5b02233
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    Electrogenerated Thin Films of Microporous Polymer Networks with Remarkably Increased Electrochemical Response to Nitroaromatic Analytes
    Palma-Cando, Alex; Scherf, Ullrich
    ACS Applied Materials & Interfaces (2015), 7 (21), 11127-11133CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Thin films of microporous polymer networks (MPNs) were generated by electrochem. polymn. of multifunctional carbazole-based monomers. The microporous films show high Brunauer-Emmett-Teller (BET) surface areas up to 1300 m2 g-1 as directly measured by Kr sorption expts. A correlation between the no. of polymerizable carbazole units of the monomer and the resulting surface area is obsd. Electrochem. sensing expts. with 1,3,5-trinitrobenzene as prototypical nitroarom. analyte demonstrate an up to 180 times increased current response of MPN-modified glassy C electrodes in relation to the nonmodified electrode. The phenomenon probably involves intermol. interactions between the electron-poor nitroarom. analytes and the electron-rich, high surface area microporous deposits, with the electrochem. redn. at the MPN-modified electrodes being an adsorption-controlled process for low scan rates. The authors expect a high application potential of such MPN-modified electrodes for boosting the sensitivity of electrochem. sensor devices.
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    Gao, M.; Tang, B. Z. Fluorescent Sensors Based on Aggregation-Induced Emission: Recent Advances and Perspectives. ACS sensors 2017, 2, 1382– 1399,  DOI: 10.1021/acssensors.7b00551
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    Fluorescent Sensors Based on Aggregation-Induced Emission: Recent Advances and Perspectives
    Gao, Meng; Tang, Ben Zhong
    ACS Sensors (2017), 2 (10), 1382-1399CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)
    A review. Fluorescent sensors with advantages of excellent sensitivity, rapid response, and easy operation are emerging as powerful tools in environmental monitoring, biol. research, and disease diagnosis. However, conventional fluorophores featured with π-planar structures usually suffer from serious self-quenching in the aggregated state, poor photostability, and small Stokes' shift. In contrast to conventional aggregation-caused quenching (ACQ) fluorophores, the newly emerged aggregation-induced emission fluorogens (AIEgens) are featured with high emission efficiency in the aggregated state, which provide unique opportunities for various sensing applications with advantages of high signal-to-noise ratio, strong photostability, and large Stokes' shift. In this review, the authors will first briefly give an introduction of the AIE concept and the turn-on sensing principles. Then, the authors will discuss the recent examples of AIE sensors according to types of analytes. Finally, the authors will give a perspective on the future developments of AIE sensors. The authors hope this review will inspire more endeavors to devote to this emerging world.
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    Wu, Y.-w.; Qin, A.-j.; Tang, B. Z. AIE-Active Polymers for Explosive Detection. Chin. J. Polym. Sci. 2017, 35, 141– 154,  DOI: 10.1007/s10118-017-1882-0
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    AIE-active polymers for explosive detection
    Wu, Yong-wei; Qin, An-jun; Tang, Ben Zhong
    Chinese Journal of Polymer Science (2017), 35 (2), 141-154CODEN: CJPSEG; ISSN:0256-7679. (Springer)
    Super-sensitive and ultra-selective detection of explosives plays a crucial role in anti-terrorism operations, homeland security, civilian safety and environment protection. Among the developed fluorescent probes, the polymers with aggregation-induced emission (AIE) characteristics have drawn much attention due to their bright emission in the aggregate and solid states. However, no review has summarized the development of AIE-active polymers for explosive detection. Herein, we reviewed the recent progress on using AIE-active polymers to detect explosives with super-amplification quenching effect. Moreover, the challenges and opportunities in this area were also briefly discussed.
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    Mahendran, V.; Pasumpon, K.; Thimmarayaperumal, S.; Thilagar, P.; Shanmugam, S. Tetraphenylethene-2-Pyrone Conjugate: Aggregation-Induced Emission Study and Explosives Sensor. J. Org. Chem. 2016, 81, 3597– 3602,  DOI: 10.1021/acs.joc.6b00267
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    Tetraphenylethene-2-Pyrone Conjugate: Aggregation-Induced Emission Study and Explosives Sensor
    Mahendran, Vaithiyanathan; Pasumpon, Kamaraj; Thimmarayaperumal, Solaimalai; Thilagar, Pakkirisamy; Shanmugam, Sivakumar
    Journal of Organic Chemistry (2016), 81 (9), 3597-3602CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
    Design and synthesis of a novel tetraphenylethene-2-pyrone (TPEP) conjugate exhibiting donor-acceptor characteristics is reported. The localized frontier MOs (DFT studies) and the solvent polarity dependent photoluminescence characteristics directly corroborate the presence of intramol. charge transfer character in TPEP. TPEP is poorly emissive in the soln. state. In contrast, upon aggregation (THF/water mixts.), TPEP exhibits aggregation-induced emission enhancement. Upon aggregation, dyad TPEP forms a fluorescent nanoaggregate which was confirmed by transmission electron microscopy imaging studies. The luminescence nanoaggregates were elegantly exploited for selective detection of nitro arom. compds. (NACs). It was found that nanoaggregates of TPEP were selectively sensing the picric acid over the other NACs. Efficiency of the quenching process was further evaluated by the Stern-Volmer equation. TPEP-based low-cost fluorescent test strips were developed for the selective detection of picric acid.
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    Mei, J.; Leung, N. L. C.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z. Aggregation-Induced Emission: Together We Shine, United We Soar!. Chem. Rev. 2015, 115, 11718– 11940,  DOI: 10.1021/acs.chemrev.5b00263
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    Aggregation-Induced Emission: Together We Shine, United We Soar!
    Mei, Ju; Leung, Nelson L. C.; Kwok, Ryan T. K.; Lam, Jacky W. Y.; Tang, Ben Zhong
    Chemical Reviews (Washington, DC, United States) (2015), 115 (21), 11718-11940CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    The United Nations has proclaimed 2015 the International Year of Light and Light-based Technologies to acknowledge the great roles of light in scientific discoveries and technol. innovations. Aggregation-induced emission, (AIE), just as its name implies, refers to a photophys. effect that light emission of a luminogen is activated by aggregate formation. The luminogens with AIE effects are called AIEgens. This article is a review of the fundamentals of the AIE phenomenon.
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    Dong, W.; Fei, T.; Palma-Cando, A.; Scherf, U. Aggregation Induced Emission and Amplified Explosive Detection of Tetraphenylethylene-Substituted Polycarbazoles. Polym. Chem. 2014, 5, 4048– 4053,  DOI: 10.1039/c4py00251b
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    Aggregation induced emission and amplified explosive detection of tetraphenylethylene-substituted polycarbazoles
    Dong, Wenyue; Fei, Teng; Palma-Cando, Alex; Scherf, Ullrich
    Polymer Chemistry (2014), 5 (13), 4048-4053CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
    Novel conjugated polymers based on 3,6-carbazole repeat units were synthesized by nickel-catalyzed Yamamoto coupling under microwave heating. The resulting poly(3,6-carbazole)s contain tetraphenylethylene (TPE) units in their side chains. The resultant polymers show aggregation induced emission (AIE) behavior. Hereby, the photoluminescence (PL) intensity of PCzTPE0.5 in 90% water-THF is 35 times higher than that in pure THF, connected to the introduction of TPE side chains. The ability of polymer PCzTPE0.5 for explosive sensing was also studied. A max. Stern-Volmer quenching const. of 1.26 × 106 M-1 was obsd. for PL quenching of PCzTPE0.5 aggregates by trinitrobenzene (TNB). A solid state paper strip test based on PCzTPE0.5 and PCzTPE also demonstrates effective PL quenching towards both TNB vapor and soln.
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    Hong, Y.; Lam, J. W. Y.; Tang, B. Z. Aggregation-Induced Emission. Chem. Soc. Rev. 2011, 40, 5361– 5388,  DOI: 10.1039/c1cs15113d
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    A review. The detection of explosives continues to be a pressing global challenge with many potential technologies being pursued by the scientific research community. Luminescence-based detection of explosive vapors with an org. semiconductor has attracted much interest because of its potential for detectors that have high sensitivity, compact form factor, simple operation and low-cost. Despite the abundance of literature on novel sensor materials systems there are relatively few mechanistic studies targeted towards vapor-based sensing. In this perspective, the progress is reviewed that has been made in understanding the processes that control the real-time luminescence quenching of thin films by analyte vapors. These are the non-radiative quenching processes by which the sensor exciton decays, the analyte-sensor intermol. binding interaction, and the diffusion process for the analyte vapors in the film. The contributions are commented of each of these processes towards the sensing response and, in particular, the relative roles of analyte diffusion and exciton diffusion. While the latter has been historically judged to be one of, if not the primary, causes for the high sensitivity of many conjugated polymers to nitrated vapors, recent evidence suggests that long exciton diffusion lengths are unnecessary. The implications of these results on the development of sensor materials for real-time detection are discussed.
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    We propose microporous networks (MPNs) of a light emitting spiro-carbazole based polymer (PSpCz) as luminescent sensor for nitro-aromatic compounds. The MPNs used in this study can be easily synthesized on arbitrarily sized/shaped substrates by simple and low-cost electrochemical deposition. The resulting MPN afford an extremely high specific surface area of 1300 m(2)/g, more than three orders of magnitude higher than that of the thin films of the respective monomer. We demonstrate, that the luminescence of PSpCz is selectively quenched by nitro-aromatic analytes, e.g. nitrobenzene, 2,4-DNT and TNT. In striking contrast to a control sample based on non-porous spiro-carbazole, which does not show any luminescence quenching upon exposure to TNT at levels of 3 ppm and below, the microporous PSpCz shows a clearly detectable response even at TNT concentrations as low as 5 ppb, clearly demonstrating the advantage of microporous films as luminescent sensors for traces of explosive analytes. This level states the vapor pressure of TNT at room temperature.
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    1,3,5-Trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) are primary components in improvised explosive devices (IEDs), but detection of these explosives in air is challenging because of their low volatility. Here the authors report the synthesis of tris(phenylene)vinylene (TPV) polymer thin films that are chem. bonded to fused SiO2 substrates bearing allyl siloxane monolayers. This procedure provides previously unavailable control over the TPV film's thickness, a crit. parameter for trace explosives detection. TPV film growth was optimized to detect RDX from the vapor phase in as little as 10 s, as well as attograms of HMX that was introduced from soln. These results suggest a balance between film thickness and the extent of the olefin metathesis reaction that influence the polymer's sensing performance. The sensitivity of TPV fluorescence to nitramine explosives is of interest for aviation and military security.
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Cite this: ACS Appl. Nano Mater. 2018, 1, 11, 6483–6492
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  • Abstract

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    Scheme 1

    Scheme 1. Schematic Illustration of the Electropolymerization of TPETCz into Fluorescent PTPETCz Thin Film, and the Fluorescence Quenching in the Presence of Trace TNT Vapors
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    Figure 1

    Figure 1. (a) CVs of monomers (0.1 mM) TPETCz (black), FLCz (red), and their 1:1 mixture (TPECz/FLCz) (blue) in dichloromethane/acetonitrile (4:1) containing 0.1 M TBAP, ITO electrodes, potential range 0–1.5 V. (b–d) First 20 consecutive CV cycles showing electropolymerization and growth of CMP thin films of (b) PTPETCz, (c) PFLCz, and (d) PTPEFLCz, ITO electrodes, prepared from corresponding monomer (0.1 mM) solutions containing 0.1 M TBAP.

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    Figure 2

    Figure 2. (a) AFM images of CMP thin film of PTPETCz grown over five CV cycles and (b, c) digital images of free-standing PTPETCz or PFLCZ thin films, respectively. Kr gas adsorption isotherms of (d) CMP thin films prepared by electropolymerization and (e) CMP powders synthesized by chemical oxidation with FeCl3; PTPETCz (navy blue), PFLCz (green), and PTPEFLCz (black), all measured at 77 K.

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    Figure 3

    Figure 3. (a) Gradual decrease of PTPETCz emission when exposed to 33 ppb of TNT vapor over time. (inset) Photographs of illuminated PTPETCz thin films on ITO (i) under UV lamp and (ii), (iii) under laser source before and after exposure to TNT, respectively. (b) Fluorescence quenching of PTPETCz films (blue) with time in the presence of TNT vapor (33 ppb), compared to the fluorescence quenching of a drop-casted monomer film (TPETCz) during exposure to TNT vapor (0.2 ppm). (inset) Photographs of illuminated TPETCz film (iv) before and (v) after TNT exposure.

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    Figure 4

    Figure 4. (a) Fluorescence quenching of a PTPETCz film with time in the presence of TNT vapor (10 ppb) and (b) degree of emission quenching of PTPETCz films when exposed to various analyte vapors; TNT (33 ppb, 3 min) and TNB (10 ppb), 1,3-DNB (47 ppb), saturated vapors of 2,4-dinitrotoluene (DNT), nitrotoluene (NT), chlorobenzene (ClBen), and toluene (Tol), exposure time 5 min. (c) Change in fluorescence intensity with time in the presence of TNT vapor (33 ppb) for PTPETCz films of ca. 61 nm thickness and (d) change in fluorescence intensity with time in the presence of TNT vapor (0.2 ppm) for PTPEFLCz films.

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      A fluorescence sensing array (or fluorescent electronic nose) is designed on a disposable paper card using 36 sets of sol. conjugated polymeric nanoparticles (SCPNs) as sensors to easily identify wide ranges of volatile analytes, including explosives and toxic industrial chems. (amines and pungent acids). A 108-dimensional vector obtained from the fluorescent color change in the sensing array is defined and directly treated as an index in a std. chem. library (30 kinds of volatile analytes and a control group). Hierarchical clustering anal. (HCA) and principal component anal. (PCA) indicated the diversity in electronic structures; satd. vapor pressure and miscibility of analytes are keys in differentiating the analytes, with electron-rich arenes and alkylamines enhancing fluorescence and electron-deficient analytes attenuating fluorescence. A support vector machine (SVM) works well to predict an unknown sample, reaching 99.5% accuracy. The excellent fluorescence stability (no fluorescence quenching after being exposed in air for one month) and high sensitivity (emission color changes within minutes when exposed to analytes) suggest that the fluorescent polymer-based electronic nose will play an important role in field detection and identification of a wide spreading of hazardous substances.
    13. 13
      Thomas, S. W.; Joly, G. D.; Swager, T. M. Chemical Sensors Based on Amplifying Fluorescent Conjugated Polymers. Chem. Rev. 2007, 107, 1339– 1386,  DOI: 10.1021/cr0501339
      13
      Chemical sensors based on amplifying fluorescent conjugated polymers
      Thomas, Samuel W., III; Joly, Guy D.; Swager, Timothy M.
      Chemical Reviews (Washington, DC, United States) (2007), 107 (4), 1339-1386CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. In this review the authors restrict the discussions to purely fluorescence-based methods using conjugated polymers. Amplification, small ion sensing using amplifying fluorescent conjugated polymers (AFPs), AFPs for detection of explosives, conjugated polyelectrolytes as biosensors, AFPs for detection of small biomols., proteins, and DNA are discussed.
    14. 14
      McQuade, D. T.; Pullen, A. E.; Swager, T. M. Conjugated Polymer-Based Chemical Sensors. Chem. Rev. 2000, 100, 2537– 2574,  DOI: 10.1021/cr9801014
      14
      Conjugated polymer-based chemical sensors
      McQuade, D. Tyler; Pullen, Anthony E.; Swager, Timothy M.
      Chemical Reviews (Washington, D. C.) (2000), 100 (7), 2537-2574CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review with 359 refs. is given on conjugated polymers with synthetic receptors and functional groups, biol. sensors, conjugated polymers with entrapped materials to aid in specificity, and unmodified conjugated polymers as sensors.
    15. 15
      Xu, Y.; Jin, S.; Xu, H.; Nagai, A.; Jiang, D. Conjugated Microporous Polymers: Design, Synthesis and Application. Chem. Soc. Rev. 2013, 42, 8012– 8031,  DOI: 10.1039/c3cs60160a
      15
      Conjugated microporous polymers: design, synthesis and application
      Xu, Yanhong; Jin, Shangbin; Xu, Hong; Nagai, Atsushi; Jiang, Donglin
      Chemical Society Reviews (2013), 42 (20), 8012-8031CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Conjugated microporous polymers (CMPs) are a class of org. porous polymers that combine π-conjugated skeletons with permanent nanopores, in sharp contrast to other porous materials that are not π-conjugated and with conventional conjugated polymers that are nonporous. As an emerging material platform, CMPs offer a high flexibility for the mol. design of conjugated skeletons and nanopores. Various chem. reactions, building blocks and synthetic methods have been developed and a broad variety of CMPs with different structures and specific properties have been synthesized, driving the rapid growth of the field. CMPs are unique in that they allow the complementary utilization of π-conjugated skeletons and nanopores for functional exploration; they have shown great potential for challenging energy and environmental issues, as exemplified by their excellent performance in gas adsorption, heterogeneous catalysis, light emitting, light harvesting and elec. energy storage. This review describes the mol. design principles of CMPs, advancements in synthetic and structural studies and the frontiers of functional exploration and potential applications.
    16. 16
      Cooper, A. I. Conjugated Microporous Polymers. Adv. Mater. 2009, 21, 1291– 1295,  DOI: 10.1002/adma.200801971
      16
      Conjugated microporous polymers
      Cooper, Andrew I.
      Advanced Materials (Weinheim, Germany) (2009), 21 (12), 1291-1295CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Conjugated microporous polymers are of great interest because they have potential to combine high surface areas in the dry state with phys. properties relevant to org. electronics. A series of recent reports has shown that materials such as poly(aryleneethynylene)s (PAEs), poly(phenylene butadiynylene)s, poly(phenylene vinylene), poly(p-phenylene)s, polysilanes, polyanilines, and polytriazines can be produced as microporous networks with apparent Brunauer-Emmett-Teller surface areas of more than 1000 m2 g-1 in some cases. Micropore size and surface area can be synthetically fine-tuned in amorphous PAE polymers and copolymers, something which was previously thought to be the preserve of ordered cryst. materials such as metal org. frameworks. We review in this Research News article recent progress made by our group and other with particular emphasis on the possible future applications of these materials.
    17. 17
      Schmidt, J.; Weber, J.; Epping, J. D.; Antonietti, M.; Thomas, A. Microporous Conjugated Poly(thienylenearylene) Networks. Adv. Mater. 2009, 21, 702– 705,  DOI: 10.1002/adma.200802692
      There is no corresponding record for this reference.
    18. 18
      Suresh, V. M.; Bonakala, S.; Roy, S.; Balasubramanian, S.; Maji, T. K. Synthesis, Characterization, and Modeling of a Functional Conjugated Microporous Polymer: CO2 Storage and Light Harvesting. J. Phys. Chem. C 2014, 118, 24369– 24376,  DOI: 10.1021/jp508734z
      18
      Synthesis, Characterization, and Modeling of a Functional Conjugated Microporous Polymer: CO2 Storage and Light Harvesting
      Suresh, Venkata M.; Bonakala, Satyanarayana; Roy, Syamantak; Balasubramanian, Sundaram; Maji, Tapas Kumar
      Journal of Physical Chemistry C (2014), 118 (42), 24369-24376CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Rationalization of structure and properties of metallic glasses porous solids at the microscopic level is essential in developing advanced materials. We delineate the structural simulation, physicochem., physicochem. of a designed tetraphenylethene-based metallic glasses conjugated microporous polymer TPE-CMP (1) and its gas storage and photophys. properties. The polymer 1 exhibits high sp. surface area of 854 m2/g. 1 showed appreciable CO2 (32.4 wt. %) uptake at 195 K up to 1 atm and 31.6 wt. % at 273 K up to 35 bar. The structural simulation, physicochem. of 1 obtained through computational methods is quant. consistent with exptl. observations. The microporous structural simulation, physicochem. of 1 was further validated by a calcn. of CO2 adsorption isotherm obtained through GCMC simulations. Quantum chem. calcns. were employed to understand the nature of interactions of CO2 with the constituents of the framework 1. π-π interaction with strength of 19 kJ/mol was obsd. between CO2 and the Ph rings of TPE. 1 shows strong turn-on greenish-yellow emission due to the restriction of Ph ring rotation of TPE node. This framework induced emission (FIE) of microporous polymer 1 is further exploited for light-harvesting applications by noncovalent encapsulation of a suitable acceptor dye, rhodamine B (RhB), in the framework.
    19. 19
      Liao, Y.; Cheng, Z.; Zuo, W.; Thomas, A.; Faul, C. F. J. Nitrogen-Rich Conjugated Microporous Polymers: Facile Synthesis, Efficient Gas Storage, and Heterogeneous Catalysis. ACS Appl. Mater. Interfaces 2017, 9, 38390– 38400,  DOI: 10.1021/acsami.7b09553
      22
      Nitrogen-Rich Conjugated Microporous Polymers: Facile Synthesis, Efficient Gas Storage, and Heterogeneous Catalysis
      Liao, Yaozu; Cheng, Zhonghua; Zuo, Weiwei; Thomas, Arne; Faul, Charl F. J.
      ACS Applied Materials & Interfaces (2017), 9 (44), 38390-38400CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Nitrogen-rich conjugated microporous polymers (NCMPs) have attracted great attention in recent years owing to their polarity, basicity, and ability to coordinate metal ions. Herein, three NCMPs, structurally close to polyaniline, were facilely synthesized via chem. oxidative polymn. between multiconnected aniline precursors. The NCMPs with high N content (11.84 wt %), intrinsic ultramicroporosity (<1 nm), and moderate surface area (485 m2 g-1) show wide-ranging adsorption functionality, e.g., CO2 uptake (11 wt %) and CO2-selectivity over N2 (360, 1 bar), 1.0 wt % H2 storage, as well as 215 wt % iodine vapor uptake at ambient pressure. Moreover, these NCMPs act as support for palladium catalysts and can maintain >94% activity in Suzuki-Miyaura coupling reactions after six continuous runs.
    20. 20
      Chang, Z.; Zhang, D.-S.; Chen, Q.; Bu, X.-H. Microporous Organic Polymers for Gas Storage and Separation Applications. Phys. Chem. Chem. Phys. 2013, 15, 5430– 5442,  DOI: 10.1039/c3cp50517k
      23
      Microporous organic polymers for gas storage and separation applications
      Chang, Ze; Zhang, Da-Shuai; Chen, Qiang; Bu, Xian-He
      Physical Chemistry Chemical Physics (2013), 15 (15), 5430-5442CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      A review. Microporous org. polymers (MOPs), an emerging class of functional porous materials featured with the pure org. component have been widely studied in recent years. These materials have potential uses in areas such as storage, sepn., and catalysis. In this Perspective, we focused on the gas storage and sepn. of MOPs. The targeted design and synthesis of MOPs toward the enhancement of gas capacity and selectivity are discussed. Furthermore, special emphasis is given to the post-synthesis modification of MOPs which have been proved to be effective methods to accurately tune the desired properties.
    21. 21
      Ben, T.; Pei, C.; Zhang, D.; Xu, J.; Deng, F.; Jing, X.; Qiu, S. Gas Storage in Porous Aromatic Frameworks (PAFs). Energy Environ. Sci. 2011, 4, 3991– 3999,  DOI: 10.1039/c1ee01222c
      24
      Gas storage in porous aromatic frameworks (PAFs)
      Ben, Teng; Pei, Cuiying; Zhang, Daliang; Xu, Jun; Deng, Feng; Jing, Xiaofei; Qiu, Shilun
      Energy & Environmental Science (2011), 4 (10), 3991-3999CODEN: EESNBY; ISSN:1754-5706. (Royal Society of Chemistry)
      A series of porous arom. frameworks (PAFs) were synthesized via a Yamamoto-type Ullmann reaction contg. quadricovalent Si (PAF-3) and Ge (PAF-4). These PAFs are thermally stable up to 465°C for PAF-3 and 443°C for PAF-4, corresponding to a 5% wt. loss according to the TG pattern. As PAF-1, they exhibit high surface areas (up to 2932 m2 g-1) and excellent adsorption ability to hydrogen, methane, and carbon dioxide. Low pressure gas uptake expts. on PAFs show PAF-3 has the highest heat of adsorption (Qst) of hydrogen (6.6 kJ mol-1) and carbon dioxide (19.2 kJ mol-1), while PAF-4 has the highest Qst for methane adsorption (23.2 kJ mol-1) among PAFs. Gas mol. recognition at 273 K was performed and results show only greenhouse gases such as carbon dioxide and methane could be adsorbed onto PAFs.
    22. 22
      Rao, K. V.; Haldar, R.; Maji, T. K.; George, S. J. Dynamic, Conjugated Microporous Polymers: Visible Light Harvesting via Guest-Responsive Reversible Swelling. Phys. Chem. Chem. Phys. 2016, 18, 156– 163,  DOI: 10.1039/C5CP05052A
      19
      Dynamic, conjugated microporous polymers: visible light harvesting via guest-responsive reversible swelling
      Rao K Venkata; Haldar Ritesh; Maji Tapas Kumar; George Subi J
      Physical chemistry chemical physics : PCCP (2016), 18 (1), 156-63 ISSN:.
      The light-harvesting properties of two fluorescent dynamic conjugated microporous organic polymers (Py-PP and Py-BPP) rendered with pyrene chromophores are described. The hydrophobic and dynamic nature of these porous frameworks allows the selective capture of various organic solvents by instantaneous swelling at room temperature. Moreover, the dynamic nature of these frameworks indicates the swelling process with visible volume expansion and enhanced fluorescence. This was further explored for the rapid encapsulation of various fluorescent chromophoric guests at room temperature and investigated for photoinduced energy transfer process. The resultant host-guest antenna materials showed efficient light-harvesting and funnelling of excitation energy of host framework towards the entrapped guest molecule. This process further yielded solid-state luminescent materials with tunable emission. This work holds a great promise on the design of smart porous organic solids from π-conjugated small molecules for optoelectronics, sensing and separation.
    23. 23
      Suresh, V. M.; Bandyopadhyay, A.; Roy, S.; Pati, S. K.; Maji, T. K. Highly Luminescent Microporous Organic Polymer with Lewis Acidic Boron Sites on the Pore Surface: Ratiometric Sensing and Capture of F(−) Ions. Chem. - Eur. J. 2015, 21, 10799– 10804,  DOI: 10.1002/chem.201500406
      20
      Highly Luminescent Microporous Organic Polymer with Lewis Acidic Boron Sites on the Pore Surface: Ratiometric Sensing and Capture of F- Ions
      Suresh, Venkata M.; Bandyopadhyay, Arkamita; Roy, Syamantak; Pati, Swapan K.; Maji, Tapas Kumar
      Chemistry - A European Journal (2015), 21 (30), 10799-10804CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Reversible and selective capture/detection of F- ions in water is of the utmost importance, as excess intake leads to adverse effects on human health. Highly robust Lewis acidic luminescent porous org. materials have potential for efficient sequestration and detection of F- ions. Herein, the rational design and synthesis of a boron-based, Lewis acidic microporous org. polymer (BMOP) derived from tris(4-bromo-2,3,5,6-tetramethylphenyl)boron nodes and diethynylbiphenyl linkers with a pore size of 1.08 nm for selective turn-on sensing and capture of F- ion are reported. The presence of a vacant pπ orbital on the boron center of BMOP results in intramol. charge transfer (ICT) from the linker to boron. BMOP shows selective turn-on blue emission for F- ions in aq. mixts. with a detection limit of 2.6 μΜ. Strong B-F interactions facilitate rapid sequestration of F- by BMOP. The ICT emission of BMOP can be reversibly regenerated by addn. of an excess of water, and the polymer can be reused several times.
    24. 24
      Chen, L.; Honsho, Y.; Seki, S.; Jiang, D. Light-Harvesting Conjugated Microporous Polymers: Rapid and Highly Efficient Flow of Light Energy with a Porous Polyphenylene Framework as Antenna. J. Am. Chem. Soc. 2010, 132, 6742– 6748,  DOI: 10.1021/ja100327h
      21
      Light-harvesting conjugated microporous polymers: rapid and highly efficient flow of light energy with a porous polyphenylene framework as antenna
      Chen, Long; Honsho, Yoshihito; Seki, Shu; Jiang, Donglin
      Journal of the American Chemical Society (2010), 132 (19), 6742-6748CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The mol. design of light-harvesting antennae requires not only the segregation of a large no. of chromophore units in a confined nanospace but also the cooperation of these units in achieving highly efficient energy transduction. This article describes the synthesis and functions of a polyphenylene-based conjugated microporous polymer (PP-CMP). PP-CMP was recently designed and synthesized by Suzuki polycondensation reaction and used as an antenna for the noncovalent construction of a light-harvesting system. In contrast to linear polyphenylene, PP-CMP consists of conjugated three-dimensional polyphenylene scaffolds and holds inherent porous structure with uniform pore size (1.56 nm) and large surface area (1083 m2 g-1). It emits blue photoluminescence, is capable of excitation energy migration over the framework, and enables rapid transportation of charge carrier with intrinsic mobility as high as 0.04 cm2 V-1 s-1. The microporous structure of PP-CMP allows for the spatial confinement of energy-accepting coumarin 6 mols. in the pores and makes the high-throughput synthesis of light-harvesting systems with designable donor-acceptor compns. possible. Excitation of the PP-CMP skeleton leads to brilliant green emission from coumarin 6, with an intensity 21-fold as high as that upon direct excitation of coumarin 6 itself, while the fluorescence from PP-CMP itself is wholly quenched as a result of energy transfer from the light-harvesting PP-CMP framework to coumarin 6. The PP-CMP skeleton is highly cooperative, with an av. of 176 phenylene units working together to channel the excitation energy to one coumarin 6 mol., and features the energy-transfer process with quick, efficient, and vectorial character. These unique characteristics clearly originate from the conjugated porous structure and demonstrate the usefulness of CMPs in the exploration of π-electronic functions, in addn. to their gas adsorption properties thus far reported.
    25. 25
      Zhao, Y.-C.; Zhou, D.; Chen, Q.; Zhang, X.-J.; Bian, N.; Qi, A.-D.; Han, B.-H. Thionyl Chloride-Catalyzed Preparation of Microporous Organic Polymers through Aldol Condensation. Macromolecules 2011, 44, 6382– 6388,  DOI: 10.1021/ma201264w
      25
      Thionyl Chloride-Catalyzed Preparation of Microporous Organic Polymers through Aldol Condensation
      Zhao, Yan-Chao; Zhou, Ding; Chen, Qi; Zhang, Xin-Jian; Bian, Ning; Qi, Ai-Di; Han, Bao-Hang
      Macromolecules (Washington, DC, United States) (2011), 44 (16), 6382-6388CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      We demonstrated the synthesis of five kinds of microporous org. polymers based on aldol self-condensation of di- and multiacetyl-contg. building blocks catalyzed by thionyl chloride. The α,β-unsatd. ketone (dimerization) and 1,3,5-trisubstituted benzene (cyclotrimerization) can be obsd. in the resulting polymers by Fourier transform IR and solid-state 13C CP/MAS NMR spectroscopy. The regular spheres and nanometer-scaled cavities were also seen from SEM and high-resoln. transmission electron microscopy images. The highest Brunauer-Emmet-Teller sp. surface area up to 832 m2 g-1 was obtained for the resulting polymers with a pore vol. of 0.48 cm3 g-1. The polymers show great hydrogen storage capacities (up to 1.56 wt %) at 77 K and 1 bar. These excellent characteristics would make them become promising candidates for heterogeneous catalysis, sepn., and gas storage.
    26. 26
      Ben, T.; Ren, H.; Ma, S.; Cao, D.; Lan, J.; Jing, X.; Wang, W.; Xu, J.; Deng, F.; Simmons, J. M.; Qiu, S.; Zhu, G. Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area. Angew. Chem., Int. Ed. 2009, 48, 9457– 9460,  DOI: 10.1002/anie.200904637
      26
      Targeted Synthesis of a Porous Aromatic Framework with High Stability and Exceptionally High Surface Area
      Ben, Teng; Ren, Hao; Ma, Shengqian; Cao, Dapeng; Lan, Jianhui; Jing, Xiaofei; Wang, Wenchuan; Xu, Jun; Deng, Feng; Simmons, Jason M.; Qiu, Shilun; Zhu, Guangshan
      Angewandte Chemie, International Edition (2009), 48 (50), 9457-9460, S9457/1-S9457/16CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      With the assistance of computational design, a porous arom. framework with an unprecedented high surface area of 7100 m2g-1 has been successfully synthesized. PAF-1 possesses local diamond-like tetrahedral bonding of tetraphenylenemethane building units to produce exceptional thermal and hydrothermal stabilities. In addn., PAF-I demonstrates high uptake capacities of hydrogen and carbon dioxide, as well as benzene and toluene vapors. The strategy presented in this work opens a new avenue for the design and construction of highly porous materials with exceptional stabilities for clean energy and environmental applications.
    27. 27
      Zhi, Y.; Li, K.; Xia, H.; Xue, M.; Mu, Y.; Liu, X. Robust Porous Organic Polymers as Efficient Heterogeneous Organo-Photocatalysts for Aerobic Oxidation Reactions. J. Mater. Chem. A 2017, 5, 8697– 8704,  DOI: 10.1039/C7TA02205K
      27
      Robust porous organic polymers as efficient heterogeneous organo-photocatalysts for aerobic oxidation reactions
      Zhi, Yongfeng; Li, Kun; Xia, Hong; Xue, Ming; Mu, Ying; Liu, Xiaoming
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (18), 8697-8704CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Metal-free, visible-light active and heterogeneous org. photocatalysts offer a more sustainable and environmentally friendly alternative to traditional metal-based catalysts. Here a porous org. hyper-crosslinked polymer, CF-HCP, was successfully synthesized through a facile and cost-effective process. The chem. and structural properties of CF-HCP were fully characterized by using powder X-ray diffraction anal., Fourier transform IR spectroscopy, 13C solid-state NMR spectroscopy, electron microscopy, thermogravimetric anal., XPS and nitrogen adsorption. The new three-dimensional hyper-crosslinked network possesses a high Brunauer-Emmett-Teller (BET) sp. surface area up to 1200 m2 g-1 with a pore vol. of 0.92 cm3 g-1, and exhibits good thermal, chem. and photochem. stability. Importantly, CF-HCP was found to be a highly effective heterogeneous photocatalyst for a wide range of org. reactions, including the oxidative coupling of primary amines, dehydrogenation of nonactive secondary amine substrates, and selective oxidn. of sulfide under visible-light irradn. and using mol. oxygen as a clean oxidant. In particular, mild reaction conditions, ease of product sepn. by simple filtration, significant recyclability and low cost make this network material an economical and eco-friendly catalyst for the prepn. of versatile org. compds.
    28. 28
      Qiao, S.; Wang, T.; Huang, W.; Jiang, J.-X.; Du, Z.; Shieh, F.-K.; Yang, R. Dendrimer-Like Conjugated Microporous Polymers. Polym. Chem. 2016, 7, 1281– 1289,  DOI: 10.1039/C5PY01767J
      28
      Dendrimer-like conjugated microporous polymers
      Qiao, Shanlin; Wang, Ting; Huang, Wei; Jiang, Jia-Xing; Du, Zhengkun; Shieh, Fa-Kuen; Yang, Renqiang
      Polymer Chemistry (2016), 7 (6), 1281-1289CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
      Four dendrimer-like polycarbazole conjugated polymer networks P-G1-T, P-G2-T, P-G1-Fo and P-G2-Fo were designed and synthesized by FeCl3 oxidative coupling polymn. Arom. thiophene and fluorenone units were employed as the linkers between carbazole units to construct the building blocks. The first generation polymers (1st) were produced from the monomers contg. two carbazole units, while the second generation polymers (2nd) were produced from the monomers with six carbazole units, which feature double oxidative polymn. sites compared with the monomers for the 1st generation. It was found that the 2nd generation polymers show a higher Brunauer-Emmett-Teller (BET) surface area and a higher gas adsorption performance than the 1st generation polymers because of more reactive sites and larger torsion angles in the monomers for the 2nd generation, which led to a highly crosslinked polymer structure and thus a high surface area. All of the polymers show high isosteric heats of CO2 adsorption over 33 kJ mol-1 because the incorporation of heteroatoms (N, S and/or O) into the skeleton of the polymers enhanced the interaction between the pore wall and CO2 mols.
    29. 29
      Chen, Q.; Liu, D.-P.; Luo, M.; Feng, L.-J.; Zhao, Y.-C.; Han, B.-H. Nitrogen-Containing Microporous Conjugated Polymers Via Carbazole-Based Oxidative Coupling Polymerization: Preparation, Porosity, and Gas Uptake. Small 2014, 10, 308– 315,  DOI: 10.1002/smll.201301618
      29
      Nitrogen-Containing Microporous Conjugated Polymers via Carbazole-Based Oxidative Coupling Polymerization: Preparation, Porosity, and Gas Uptake
      Chen, Qi; Liu, De-Peng; Luo, Min; Feng, Li-Juan; Zhao, Yan-Chao; Han, Bao-Hang
      Small (2014), 10 (2), 308-315CODEN: SMALBC; ISSN:1613-6810. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Facile prepn. of microporous conjugated polycarbazoles via carbazole-based oxidative coupling polymn. is reported. The process to form the polymer network has cost-effective advantages such as using a cheap catalyst, mild reaction conditions, and requiring a single monomer. Because no other functional groups such as halo groups, boric acid, and alkyne are required for coupling polymn., properties derived from monomers are likely to be fully retained and structures of final polymers are easier to characterize. A series of microporous conjugated polycarbazoles (CPOP-2-7) with permanent porosity are synthesized using versatile carbazolyl-bearing 2D and 3D conjugated core structures with non-planar rigid conformation as building units. The Brunauer-Emmett-Teller sp. surface area values for these porous materials vary between 510 and 1430 M2 g-1. The dominant pore sizes of the polymers based on the different building blocks are located between 0.59 and 0.66 nm. Gas (H2 and CO2) adsorption isotherms show that CPOP-7 exhibits the best uptake capacity for hydrogen (1.51% at 1.0 bar and 77 K) and carbon dioxide (13.2% at 1.0 bar and 273 K) among the obtained polymers. Furthermore, its high CH4/N2 and CO2/N2 adsorption selectivity gives polymer CPOP-7 potential application in gas sepn.
    30. 30
      Bandyopadhyay, S.; Pallavi, P.; Anil, A. G.; Patra, A. Fabrication of Porous Organic Polymers in the Form of Powder, Soluble in Organic Solvents and Nanoparticles: A Unique Platform for Gas Adsorption and Efficient Chemosensing. Polym. Chem. 2015, 6, 3775– 3780,  DOI: 10.1039/C5PY00235D
      30
      Fabrication of porous organic polymers in the form of powder, soluble in organic solvents and nanoparticles: a unique platform for gas adsorption and efficient chemosensing
      Bandyopadhyay, Sujoy; Pallavi, Pragyan; Anil, Amith G.; Patra, Abhijit
      Polymer Chemistry (2015), 6 (20), 3775-3780CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
      Conjugated porous org. polymers based on a novel core of tetraphenyl-5,5-dioctylcyclopentadiene (TPDC) have been fabricated in the form of powder (P1), sol. in common org. solvents (P2) as well as aq. dispersion of nanoparticles (P3). Fine tuning of the conditions of polycondensation reactions involving tetrakis(4-bromophenyl)-5,5-dioctylcyclopentadiene and diethynylbenzene leads to the formation of TPDC based polymers in three different forms. P1, P2 and P3 possess high thermal stability (up to 375°C) and are porous in nature. The Brunauer-Emmett-Teller (BET) surface area and total pore vol. of P1 were estd. to be 405 m2 g-1 and 0.68 cm3 g-1 resp. Solid P1 was explored for hydrogen and carbon dioxide adsorption. Soln. of P2 and aq. dispersion of P3 exhibit strong cyan fluorescence and are applied for the sensing of nitroaroms. Steady state and time resolved fluorescence measurements reveal the underlying photophysics of amplified fluorescence quenching of P2 and P3 by nitroaroms. Porosity, gas adsorption, as well as soly., strong fluorescence and sensing capabilities establish TPDC based porous polymers as new multifunctional materials and can find broad applications in sensing and optical devices.
    31. 31
      Li, Z.; Li, H.; Xia, H.; Ding, X.; Luo, X.; Liu, X.; Mu, Y. Triarylboron-Linked Conjugated Microporous Polymers: Sensing and Removal of Fluoride Ions. Chem. - Eur. J. 2015, 21, 17355– 17362,  DOI: 10.1002/chem.201502241
      31
      Triarylboron-Linked Conjugated Microporous Polymers: Sensing and Removal of Fluoride Ions
      Li, Zhongping; Li, He; Xia, Hong; Ding, Xuesong; Luo, Xiaolong; Liu, Xiaoming; Mu, Ying
      Chemistry - A European Journal (2015), 21 (48), 17355-17362CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A luminescent conjugated microporous polymer (BCMP-3) has been synthesized in high yield by a carbon-carbon coupling reaction using triarylboron as a building unit. BCMP-3 was fully characterized by using powder x-ray diffraction anal., Fourier transform IR spectroscopy, 13C solid-state NMR spectroscopy, field emission SEM, thermogravimetric anal., and nitrogen and carbon dioxide adsorption. The new three-dimensional conjugated framework possess a high Brunauer-Emmett-Teller (BET) sp. surface area up to 950 M2 g-1 with a pore vol. of 0.768 Cm3 g-1, good stability, and abundant boron sites in the skeleton. Under excited-light irradn., BCMP-3 exhibits strong fluorescent emission at 488 nm with a high abs. quantum yield of 18 % in the solid state. Polymer BCMP-3 acts as a colorimetric and fluorescent chemosensor with high sensitivity and selectivity for F- over other common anions. In addn., the polymer also works as an adsorbent for F- removal and shows good adsorption capacities of up to 24 mg g-1 at equil. F- concns. of 16 mg L-1 and a temp. of 298 K. The adsorption kinetics and isotherm were analyzed by fitting exptl. data with pseudo-second-order kinetics and Langmuir equations. Furthermore, we highlight that BCMP-3 is an adsorbent for fluoride removal that can be efficiently reused many times without loss of adsorption efficiency.
    32. 32
      Xiang, L.; Zhu, Y.; Gu, S.; Chen, D.; Fu, X.; Zhang, Y.; Yu, G.; Pan, C.; Hu, Y. A Luminescent Hypercrosslinked Conjugated Microporous Polymer for Efficient Removal and Detection of Mercury Ions. Macromol. Rapid Commun. 2015, 36, 1566– 1571,  DOI: 10.1002/marc.201500159
      32
      A Luminescent Hypercrosslinked Conjugated Microporous Polymer for Efficient Removal and Detection of Mercury Ions
      Xiang, Lu; Zhu, Yunlong; Gu, Shuai; Chen, Dongyang; Fu, Xian; Zhang, Yindong; Yu, Guipeng; Pan, Chunyue; Hu, Yuehua
      Macromolecular Rapid Communications (2015), 36 (17), 1566-1571CODEN: MRCOE3; ISSN:1022-1336. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A hypercrosslinked conjugated microporous polymer (HCMP-1) with a robustly efficient absorption and highly specific sensitivity to mercury ions (Hg2+) is synthesized in a one-step Friedel-Crafts alkylation of cost-effective 2,4,6-trichloro-1,3,5-triazine and dibenzofuran in 1,2-dichloroethane. HCMP-1 has a moderate Brunauer-Emmett-Teller sp. surface (432 m2 g-1), but it displays a high adsorption affinity (604 mg g-1) and excellent trace efficiency for Hg2+. The π-π* electronic transition among the arom. heterocyclic rings endows HCMP-1 a strong fluorescent property and the fluorescence is obviously weakened after Hg2+ uptake, which makes the hypercrosslinked conjugated microporous polymer a promising fluorescent probe for Hg2+ detection, owning a super-high sensitivity (detection limit 5 × 10-8 mol L-1).
    33. 33
      Liu, J.; Yee, K.-K.; Lo, K. K.-W.; Zhang, K. Y.; To, W.-P.; Che, C.-M.; Xu, Z. Selective Ag(I) Binding, H2S Sensing, and White-Light Emission from an Easy-To-Make Porous Conjugated Polymer. J. Am. Chem. Soc. 2014, 136, 2818– 2824,  DOI: 10.1021/ja411067a
      33
      Selective Ag(I) Binding, H2S Sensing, and White-Light Emission from an Easy-to-Make Porous Conjugated Polymer
      Liu, Jie; Yee, Ka-Kit; Lo, Kenneth Kam-Wing; Zhang, Kenneth Yin; To, Wai-Pong; Che, Chi-Ming; Xu, Zhengtao
      Journal of the American Chemical Society (2014), 136 (7), 2818-2824CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Sepg. silver (Ag+) from lead (Pb2+) is one of the many merits of the porous polymer framework reported here. The selective metal binding stems from the well-defined chelating unit of N-heterocycles, which consists of a triazine (C3N3) ring bonded to three 3,5-dimethylpyrazole moieties. Such a rigid and open triad also serves as the distinct building unit in the fully conjugated 3D polymer scaffold. Because of its strong fluorescence and porosity (e.g., BET surface area: 355 m2/g), and because of the various types of metal species that can be readily taken up, this versatile framework is esp. fit for functionalization. For example, with AgNO3 loaded, the framework solid exhibits a brown color in response to water solns. of H2S, even at the diln. of 5.0 μM (0.17 ppm); whereas cysteine and other biol. relevant thiols do not cause notable change in color. In another example, tunable white-light emission was produced when an Ir(III) complex was doped (e.g., about 0.02% of the polymer wt.) onto the framework. Mechanistically, the bound Ir(III) centers become highly emissive in the orange-red region, complementing the broad, bluish emission from the polymer host to result in the overall white-light quality: the color attributes of the emission are therefore easily tunable by the Ir(III) dopant concn. With this exemplary study, we intend to highlight metal uptake as an effective approach to modify and enrich the properties of porous polymer frameworks and to stimulate interest in further examg. metal-polymer interactions in the context of sensing, sepn., catalyzes, and other applications.
    34. 34
      Gopalakrishnan, D.; Dichtel, W. R. Direct Detection of RDX Vapor Using a Conjugated Polymer Network. J. Am. Chem. Soc. 2013, 135, 8357– 8362,  DOI: 10.1021/ja402668e
      34
      Direct Detection of RDX Vapor Using a Conjugated Polymer Network
      Gopalakrishnan, Deepti; Dichtel, William R.
      Journal of the American Chemical Society (2013), 135 (22), 8357-8362CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) is a principal component of plastic explosives used in acts of terrorism and within improvised explosive devices, among others. Approaches to detect RDX compatible with remote, "stand-off" sampling that do not require preconcn. strategies, such as the swabs commonly employed in airports, will benefit military and civilian security. Such detection remains a significant challenge because RDX is 103 less volatile than 1,3,5-trinitrotoluene (TNT), corresponding to a parts-per-trillion vapor pressure under ambient conditions. Therefore, while fluorescence quenching of conjugated polymers is sufficiently sensitive to detect TNT vapors, RDX vapor detection is undemonstrated. Here the authors report a crosslinked phenylene vinylene polymer network whose fluorescence is quenched by trace amts. of RDX introduced from soln. or the vapor phase. Fluorescence quenching is reduced, but remains significant, when partially degraded RDX is employed, suggesting that the polymer responds to RDX itself. The polymer network also responds to TNT and PETN similarly introduced from soln. or the vapor phase. Pure solvents, volatile amines, and the outgassed vapors from lipstick or sunscreen do not quench polymer fluorescence. The established success of TNT sensors based on fluorescence quenching makes this a material of interest for real-world explosive sensors and will motivate further interest in crosslinked polymers and framework materials for sensing applications.
    35. 35
      Liu, X.; Xu, Y.; Jiang, D. Conjugated Microporous Polymers as Molecular Sensing Devices: Microporous Architecture Enables Rapid Response and Enhances Sensitivity in Fluorescence-On and Fluorescence-Off Sensing. J. Am. Chem. Soc. 2012, 134, 8738– 8741,  DOI: 10.1021/ja303448r
      35
      Conjugated Microporous Polymers as Molecular Sensing Devices: Microporous Architecture Enables Rapid Response and Enhances Sensitivity in Fluorescence-On and Fluorescence-Off Sensing
      Liu, Xiaoming; Xu, Yanhong; Jiang, Donglin
      Journal of the American Chemical Society (2012), 134 (21), 8738-8741CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      Conjugated polymers are attractive materials for the detection of chems. because of their remarkable π-conjugation and photoluminescence properties. The authors report a new strategy for the construction of mol. detection systems with conjugated microporous polymers (CMPs). The condensation of a carbazole deriv., TCB, gives a conjugated microporous polymer (TCB-CMP) that exhibits blue luminescence and possesses a large surface area. Compared with a linear polymer analog, TCB-CMP showed enhanced detection sensitivity and allowed for the rapid detection of arenes upon exposure to their vapors. TCB-CMP displayed prominent fluorescence enhancement in the presence of electron-rich arene vapors and drastic fluorescence quenching in the presence of electron-deficient arene vapors, and it could be reused without a loss of sensitivity and responsiveness. These characteristics are attributed to the microporous conjugated network of the material. Specifically, the micropores absorb arene mols. into the confined space of the polymer, the skeleton possesses a large surface area and provides a broad interface for arenes, and the network architecture facilitates exciton migration over the framework. These structural features function cooperatively, enhancing the signaling activity of TCB-CMP in fluorescence-on and fluorescence-off detection.
    36. 36
      Patra, A.; Scherf, U. Fluorescent Microporous Organic Polymers: Potential Testbed for Optical Applications. Chem. - Eur. J. 2012, 18, 10074– 10080,  DOI: 10.1002/chem.201200804
      36
      Fluorescent Microporous Organic Polymers: Potential Testbed for Optical Applications
      Patra, Abhijit; Scherf, Ullrich
      Chemistry - A European Journal (2012), 18 (33), 10074-10080CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Fluorescent microporous org. polymers (MOPs) are an emerging class of porous org. materials with considerable technol. relevance due to great promise in a range of applications. In this respect, innovative optical materials have been developed based on MOPs. In this article, a brief appraisal of the fabrication methodologies of fluorescent MOPs, their optical attributes, and promising application potentials are presented.
    37. 37
      Wang, D.; Sun, R.; Feng, S.; Li, W.; Liu, H. Retrieving the Original Appearance of Polyhedral Oligomeric Silsesquioxane-Based Porous Polymers. Polymer 2017, 130, 218– 229,  DOI: 10.1016/j.polymer.2017.10.021
      37
      Retrieving the original appearance of polyhedral oligomeric silsesquioxane-based porous polymers
      Wang, Dengxu; Sun, Ruixue; Feng, Shengyu; Li, Wensi; Liu, Hongzhi
      Polymer (2017), 130 (), 218-229CODEN: POLMAG; ISSN:0032-3861. (Elsevier Ltd.)
      A class of polyhedral oligomeric silsesquioxane (POSS)-based porous polymers contg. typical π-conjugated units, including biphenyl, tetrahedral silicon-centered units and tetraphenylethene, have been prepd. by Heck reactions of octavinylsilsesquioxane (OVS) with the corresponding brominated monomers. Two sets of reaction conditions were employed to retrieve their original appearance. These materials exhibit tunable appearance with the colors from dark colors to various colors and the phys. forms from coarse powders with irregular shape particles to fine powders with relatively uniform solid spheres by altering the reaction conditions from method A to method B. It is found that the variation of appearance leads to the alteration of the fluorescence from nearly no fluorescence to bright fluorescence. Considering the conjugated feature of these polymers, we speculate that these polymers were afforded as their original appearance by method B. This finding could explain the unexpected phenomenon that many conjugated porous polymers exhibit no or very low fluorescence despite of their π-conjugated structures, i.e., their real appearance may be covered by the residuals in the networks. Thus, researchers should deliberately consider the material's appearance when prepg. fluorescent porous polymers. Addnl., samples with fine powders show excellent dispersion stability in solvents, which is beneficial for the use of these materials in soln. processable methodologies such as spin-coating. Furthermore, these materials show efficient fluorescence quenching for nitrobenzene vapor in thin films, thereby indicating their potential application as sensing agents for the detection of explosives.
    38. 38
      Ko, J. H.; Moon, J. H.; Kang, N.; Park, J. H.; Shin, H.-W.; Park, N.; Kang, S.; Lee, S. M.; Kim, H. J.; Ahn, T. K.; Lee, J. Y.; Son, S. U. Engineering of Sn-Porphyrin Networks on the Silica Surface: Sensing of Nitrophenols in Water. Chem. Commun. (Cambridge, U. K.) 2015, 51, 8781– 8784,  DOI: 10.1039/C5CC02144H
      38
      Engineering of Sn-porphyrin networks on the silica surface: sensing of nitrophenols in water
      Ko, Ju Hong; Moon, Jong Hun; Kang, Narae; Park, Joon Hyun; Shin, Hee-Won; Park, Nojin; Kang, Sungah; Lee, Sang Moon; Kim, Hae Jin; Ahn, Tae Kyu; Lee, Jin Yong; Son, Seung Uk
      Chemical Communications (Cambridge, United Kingdom) (2015), 51 (42), 8781-8784CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Sn-porphyrin networks were engineered on the surface of a thin layer chromatog. (TLC) plate via Sonogashira coupling of the Sn-porphyrin building block and 1,4-diiodobenzene. The Sn-porphyrin film showed a strong Soret band absorption at 422 nm, emission at 600-630 nm, and excellent sensing performance toward nitrophenols in water.
    39. 39
      Sun, R.; Huo, X.; Lu, H.; Feng, S.; Wang, D.; Liu, H. Recyclable Fluorescent Paper Sensor for Visual Detection of Nitroaromatic Explosives. Sens. Actuators, B 2018, 265, 476– 487,  DOI: 10.1016/j.snb.2018.03.072
      39
      Recyclable fluorescent paper sensor for visual detection of nitroaromatic explosives
      Sun, Ruixue; Huo, Xiaojuan; Lu, Hang; Feng, Shengyu; Wang, Dengxu; Liu, Hongzhi
      Sensors and Actuators, B: Chemical (2018), 265 (), 476-487CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
      Development of rapid, sensitive, and visual detection of nitroarom. explosives is of great importance for homeland security and human safety. Herein, three novel fluorescent nanoporous polymers (FNPs), HPP-1-HPP-3, were first prepd. by Heck reactions of octavinylsilsesquioxane with ethene derivs. contg. bis-, tri-, or tetrakis- bromophenyl groups. Based on highly sensitive detection of explosives, including p-nitrotoluene (NT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), 4-nitrophenol (NP), 2,4-dinitrophenol (DNP) and picric acid (PA), and high selectivity for detecting TNT and PA, by HPP-2 dispersion in ethanol, a fluorescent paper sensor was developed by a new fabrication process, i.e., vacuum filtrating of HPP-2 dispersion in ethanol, followed by washing and natural drying. The resultant paper sensor was found to be sensitive to explosives in the soln., solid and vapor phase with a rapid response time of < 10 s by visually observing the fluorescence quenching phenomenon. Moreover, this paper sensor is recyclable with desirable fluorescence resuming ratio, which is higher than 75% after 10 times recycle detection. This developed paper sensor is promisingly applied for rapid, on-site and visual sensing of explosive residuals. The remarkable fluorescence and reusability of this sensor could be expanded to other fluorescence detection of residuals.
    40. 40
      Palma-Cando, A.; Preis, E.; Scherf, U. Silicon- or Carbon-Cored Multifunctional Carbazolyl Monomers for the Electrochemical Generation of Microporous Polymer Films. Macromolecules 2016, 49, 8041– 8047,  DOI: 10.1021/acs.macromol.6b02025
      There is no corresponding record for this reference.
    41. 41
      Gu, C.; Huang, N.; Wu, Y.; Xu, H.; Jiang, D. Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity. Angew. Chem., Int. Ed. 2015, 54, 11540– 11544,  DOI: 10.1002/anie.201504786
      41
      Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity
      Gu, Cheng; Huang, Ning; Wu, Yang; Xu, Hong; Jiang, Donglin
      Angewandte Chemie, International Edition (2015), 54 (39), 11540-11544CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Porous org. polymers allow the integration of various π-units into robust porous π-networks, but they are usually synthesized as unprocessable solids with poor light-emitting performance as a result of aggregation-related excitation dissipation. Herein, we report a general strategy for the synthesis of highly emissive photofunctional porous polymer films on the basis of a complementary scheme for the structural design of aggregation-induced-emissive π-systems. We developed a high-throughput and facile method for the direct synthesis of large-area porous thin films at the liq.-electrode interface. The approach enables the prepn. of microporous films within only a few seconds or minutes and allows precise control over their thickness with sub-nanometer precision. By virtue of rapid photoinduced electron transfer, the thin films can detect explosives with enhanced sensitivity to low parts-per-million levels in a selective manner.
    42. 42
      Palma-Cando, A.; Brunklaus, G.; Scherf, U. Thiophene-Based Microporous Polymer Networks via Chemical or Electrochemical Oxidative Coupling. Macromolecules 2015, 48, 6816– 6824,  DOI: 10.1021/acs.macromol.5b01821
      42
      Thiophene-Based Microporous Polymer Networks via Chemical or Electrochemical Oxidative Coupling
      Palma-Cando, Alex; Brunklaus, Gunther; Scherf, Ullrich
      Macromolecules (Washington, DC, United States) (2015), 48 (19), 6816-6824CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Four thiophene-based monomers were synthesized by Stille- or Suzuki-type couplings followed by chem. or electrochem. polymn. into microporous polymer networks (MPNs) with high BET surface areas (SBET). Similar SBET values of up to 2020 and 2135 m2 g-1 were detd. for tetraphenylmethane-cored bulk MPN powders and thin films, resp. Electrochem. polymn. in boron trifluoride di-Et etherate (BFEE)/dichloromethane (DCM) mixts. allows for the generation of MPN films with optimized porosity. Moreover, an interesting effect of boron trifluoride on the connectivity of the monomeric units during electropolymn. is obsd. for 3-thienyl-based monomers. Finally, the electrochem. redn. of 1,3,5-trinitrobenzene at MPN-modified glassy carbon (GC) electrodes shows increased cathodic responses compared to non-modified GC electrodes due to interaction between electron-deficient nitroarom. analyte and electron-rich MPN film. The influence of the sp. surface area of MPNs on the electrochem. response is also studied for this class of materials.
    43. 43
      Zhang, H.; Zhang, Y.; Gu, C.; Ma, Y. Electropolymerized Conjugated Microporous Poly(zinc-porphyrin) Films as Potential Electrode Materials in Supercapacitors. Adv. Energy Mater. 2015, 5, 1402175,  DOI: 10.1002/aenm.201402175
      There is no corresponding record for this reference.
    44. 44
      Carbas, B. B.; Odabas, S.; Türksoy, F.; Tanyeli, C. Synthesıs of a New Electrochromıc Polymer Based on Tetraphenylethylene Cored Tetrakıs Carbazole Complex and its Electrochromıc Devıce Application. Electrochim. Acta 2016, 193, 72– 79,  DOI: 10.1016/j.electacta.2016.02.024
      There is no corresponding record for this reference.
    45. 45
      Gu, C.; Huang, N.; Chen, Y.; Zhang, H.; Zhang, S.; Li, F.; Ma, Y.; Jiang, D. Porous Organic Polymer Films with Tunable Work Functions and Selective Hole and Electron Flows for Energy Conversions. Angew. Chem., Int. Ed. 2016, 55, 3049– 3053,  DOI: 10.1002/anie.201510723
      45
      Porous Organic Polymers Films with Tunable Work Functions and Selective Hole and Electron Flows for Energy Conversions
      Gu, Cheng; Huang, Ning; Chen, Youchun; Zhang, Huanhuan; Zhang, Shitong; Li, Fenghong; Ma, Yuguang; Jiang, Donglin
      Angewandte Chemie, International Edition (2016), 55 (9), 3049-3053CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Org. optoelectronics are promising technologies for energy conversion. However, the electrode interlayer, a key material between active layers and conducting electrodes that controls the transport of charge carriers in and out of devices, is still a chem. challenge. Herein, we report a class of porous org. polymers with tunable work function as hole- and electron-selective electrode interlayers. The network with organoborane and carbazole units exhibits extremely low work-function-selective electron flow, while upon ionic ligation and electro-oxidn., the network significantly increases the work function and turns into hole conduction. We demonstrate their outstanding functions as anode and cathode interlayers in energy-converting solar cells and light-emitting diodes.
    46. 46
      Gu, C.; Huang, N.; Chen, Y.; Qin, L.; Xu, H.; Zhang, S.; Li, F.; Ma, Y.; Jiang, D. π-Conjugated Microporous Polymer Films: Designed Synthesis, Conducting Properties, and Photoenergy Conversions. Angew. Chem., Int. Ed. 2015, 54, 13594– 13598,  DOI: 10.1002/anie.201506570
      46
      π-Conjugated Microporous Polymer Films: Designed Synthesis, Conducting Properties, and Photoenergy Conversions
      Gu, Cheng; Huang, Ning; Chen, Youchun; Qin, Leiqiang; Xu, Hong; Zhang, Shitong; Li, Fenghong; Ma, Yuguang; Jiang, Donglin
      Angewandte Chemie, International Edition (2015), 54 (46), 13594-13598CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Conjugated microporous polymers are a unique class of polymers that combine extended π-conjugation with inherent porosity. However, these polymers are synthesized through soln.-phase reactions to yield insol. and unprocessable solids, which preclude not only the evaluation of their conducting properties but also the fabrication of thin films for device implementation. Here, we report a strategy for the synthesis of thin films of π-conjugated microporous polymers by designing thiophene-based electropolymn. at the soln.-electrode interface. High-quality films are prepd. on a large area of various electrodes, the film thickness is controllable, and the films are used for device fabrication. These films are outstanding hole conductors and, upon incorporation of fullerenes into the pores, function as highly efficient photoactive layers for energy conversions. Our film strategy may boost the applications in photocatalysis, energy storage, and optoelectronics.
    47. 47
      Gu, C.; Chen, Y.; Zhang, Z.; Xue, S.; Sun, S.; Zhang, K.; Zhong, C.; Zhang, H.; Pan, Y.; Lv, Y.; Yang, Y.; Li, F.; Zhang, S.; Huang, F.; Ma, Y. Electrochemical Route to Fabricate Film-Like Conjugated Microporous Polymers and Application for Organic Electronics. Adv. Mater. 2013, 25, 3443– 3448,  DOI: 10.1002/adma.201300839
      47
      Electrochemical Route to Fabricate Film-Like Conjugated Microporous Polymers (CMPs) and Application for Organic Electronics
      Gu, Cheng; Chen, Youchun; Zhang, Zhongbo; Xue, Shanfeng; Sun, Shuheng; Zhang, Kai; Zhong, Chengmei; Zhang, Huanhuan; Pan, Yuyu; Lv, Ying; Yang, Yanqin; Li, Fenghong; Zhang, Suobo; Huang, Fei; Ma, Yuguang
      Advanced Materials (Weinheim, Germany) (2013), 25 (25), 3443-3448CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Authors report a novel strategy to fabricate CMP films electrochem., and highlight the application of CMP films in electronic devices. Electropolymn. (EP) with concurrent polymer film deposition has proven to be an expecially useful method to process cross-linked polymer network films. The authors intentionally synthesized the EP precursor TPTCz, which combines a tetrahedral tetraphenylmethane core and four peripheral carbazole groups.
    48. 48
      Palma-Cando, A.; Scherf, U. Electrochemically Generated Thin Films of Microporous Polymer Networks: Synthesis, Properties, and Applications. Macromol. Chem. Phys. 2016, 217, 827– 841,  DOI: 10.1002/macp.201500484
      48
      Electrochemically Generated Thin Films of Microporous Polymer Networks: Synthesis, Properties, and Applications
      Palma-Cando, Alex; Scherf, Ullrich
      Macromolecular Chemistry and Physics (2016), 217 (7), 827-841CODEN: MCHPES; ISSN:1022-1352. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A review. Electrochem. oxidative polymn. of rigid, multifunctional monomers allows for the synthesis of microporous thin films with high surface areas. Multifunctional, carbazole- and thiophene-based rigid monomers were utilized as rigid 3D building blocks (tectons) toward microporous polymer films with relatively smooth surface morphol. Within the last four years, several studies following this approach were published that report interesting results on the application of these electrogenerated films in org. electronics, photoluminescence-based or electrochem. chemodetectors, electrochem. supercapacitors, and light-harvesting antennae for exciton pumping. In this work, the synthetic approaches for the electrochem. polymn. of multifunctional carbazole- and thiophene-based tectons and resulting properties and application possibilities of the electrogenerated microporous polymer films are reviewed.
    49. 49
      Palma-Cando, A.; Scherf, U. Electrogenerated Thin Films of Microporous Polymer Networks with Remarkably Increased Electrochemical Response to Nitroaromatic Analytes. ACS Appl. Mater. Interfaces 2015, 7, 11127– 11133,  DOI: 10.1021/acsami.5b02233
      49
      Electrogenerated Thin Films of Microporous Polymer Networks with Remarkably Increased Electrochemical Response to Nitroaromatic Analytes
      Palma-Cando, Alex; Scherf, Ullrich
      ACS Applied Materials & Interfaces (2015), 7 (21), 11127-11133CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Thin films of microporous polymer networks (MPNs) were generated by electrochem. polymn. of multifunctional carbazole-based monomers. The microporous films show high Brunauer-Emmett-Teller (BET) surface areas up to 1300 m2 g-1 as directly measured by Kr sorption expts. A correlation between the no. of polymerizable carbazole units of the monomer and the resulting surface area is obsd. Electrochem. sensing expts. with 1,3,5-trinitrobenzene as prototypical nitroarom. analyte demonstrate an up to 180 times increased current response of MPN-modified glassy C electrodes in relation to the nonmodified electrode. The phenomenon probably involves intermol. interactions between the electron-poor nitroarom. analytes and the electron-rich, high surface area microporous deposits, with the electrochem. redn. at the MPN-modified electrodes being an adsorption-controlled process for low scan rates. The authors expect a high application potential of such MPN-modified electrodes for boosting the sensitivity of electrochem. sensor devices.
    50. 50
      Gao, M.; Tang, B. Z. Fluorescent Sensors Based on Aggregation-Induced Emission: Recent Advances and Perspectives. ACS sensors 2017, 2, 1382– 1399,  DOI: 10.1021/acssensors.7b00551
      50
      Fluorescent Sensors Based on Aggregation-Induced Emission: Recent Advances and Perspectives
      Gao, Meng; Tang, Ben Zhong
      ACS Sensors (2017), 2 (10), 1382-1399CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)
      A review. Fluorescent sensors with advantages of excellent sensitivity, rapid response, and easy operation are emerging as powerful tools in environmental monitoring, biol. research, and disease diagnosis. However, conventional fluorophores featured with π-planar structures usually suffer from serious self-quenching in the aggregated state, poor photostability, and small Stokes' shift. In contrast to conventional aggregation-caused quenching (ACQ) fluorophores, the newly emerged aggregation-induced emission fluorogens (AIEgens) are featured with high emission efficiency in the aggregated state, which provide unique opportunities for various sensing applications with advantages of high signal-to-noise ratio, strong photostability, and large Stokes' shift. In this review, the authors will first briefly give an introduction of the AIE concept and the turn-on sensing principles. Then, the authors will discuss the recent examples of AIE sensors according to types of analytes. Finally, the authors will give a perspective on the future developments of AIE sensors. The authors hope this review will inspire more endeavors to devote to this emerging world.
    51. 51
      Wu, Y.-w.; Qin, A.-j.; Tang, B. Z. AIE-Active Polymers for Explosive Detection. Chin. J. Polym. Sci. 2017, 35, 141– 154,  DOI: 10.1007/s10118-017-1882-0
      51
      AIE-active polymers for explosive detection
      Wu, Yong-wei; Qin, An-jun; Tang, Ben Zhong
      Chinese Journal of Polymer Science (2017), 35 (2), 141-154CODEN: CJPSEG; ISSN:0256-7679. (Springer)
      Super-sensitive and ultra-selective detection of explosives plays a crucial role in anti-terrorism operations, homeland security, civilian safety and environment protection. Among the developed fluorescent probes, the polymers with aggregation-induced emission (AIE) characteristics have drawn much attention due to their bright emission in the aggregate and solid states. However, no review has summarized the development of AIE-active polymers for explosive detection. Herein, we reviewed the recent progress on using AIE-active polymers to detect explosives with super-amplification quenching effect. Moreover, the challenges and opportunities in this area were also briefly discussed.
    52. 52
      Mahendran, V.; Pasumpon, K.; Thimmarayaperumal, S.; Thilagar, P.; Shanmugam, S. Tetraphenylethene-2-Pyrone Conjugate: Aggregation-Induced Emission Study and Explosives Sensor. J. Org. Chem. 2016, 81, 3597– 3602,  DOI: 10.1021/acs.joc.6b00267
      52
      Tetraphenylethene-2-Pyrone Conjugate: Aggregation-Induced Emission Study and Explosives Sensor
      Mahendran, Vaithiyanathan; Pasumpon, Kamaraj; Thimmarayaperumal, Solaimalai; Thilagar, Pakkirisamy; Shanmugam, Sivakumar
      Journal of Organic Chemistry (2016), 81 (9), 3597-3602CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
      Design and synthesis of a novel tetraphenylethene-2-pyrone (TPEP) conjugate exhibiting donor-acceptor characteristics is reported. The localized frontier MOs (DFT studies) and the solvent polarity dependent photoluminescence characteristics directly corroborate the presence of intramol. charge transfer character in TPEP. TPEP is poorly emissive in the soln. state. In contrast, upon aggregation (THF/water mixts.), TPEP exhibits aggregation-induced emission enhancement. Upon aggregation, dyad TPEP forms a fluorescent nanoaggregate which was confirmed by transmission electron microscopy imaging studies. The luminescence nanoaggregates were elegantly exploited for selective detection of nitro arom. compds. (NACs). It was found that nanoaggregates of TPEP were selectively sensing the picric acid over the other NACs. Efficiency of the quenching process was further evaluated by the Stern-Volmer equation. TPEP-based low-cost fluorescent test strips were developed for the selective detection of picric acid.
    53. 53
      Mei, J.; Leung, N. L. C.; Kwok, R. T. K.; Lam, J. W. Y.; Tang, B. Z. Aggregation-Induced Emission: Together We Shine, United We Soar!. Chem. Rev. 2015, 115, 11718– 11940,  DOI: 10.1021/acs.chemrev.5b00263
      53
      Aggregation-Induced Emission: Together We Shine, United We Soar!
      Mei, Ju; Leung, Nelson L. C.; Kwok, Ryan T. K.; Lam, Jacky W. Y.; Tang, Ben Zhong
      Chemical Reviews (Washington, DC, United States) (2015), 115 (21), 11718-11940CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      The United Nations has proclaimed 2015 the International Year of Light and Light-based Technologies to acknowledge the great roles of light in scientific discoveries and technol. innovations. Aggregation-induced emission, (AIE), just as its name implies, refers to a photophys. effect that light emission of a luminogen is activated by aggregate formation. The luminogens with AIE effects are called AIEgens. This article is a review of the fundamentals of the AIE phenomenon.
    54. 54
      Dong, W.; Fei, T.; Palma-Cando, A.; Scherf, U. Aggregation Induced Emission and Amplified Explosive Detection of Tetraphenylethylene-Substituted Polycarbazoles. Polym. Chem. 2014, 5, 4048– 4053,  DOI: 10.1039/c4py00251b
      54
      Aggregation induced emission and amplified explosive detection of tetraphenylethylene-substituted polycarbazoles
      Dong, Wenyue; Fei, Teng; Palma-Cando, Alex; Scherf, Ullrich
      Polymer Chemistry (2014), 5 (13), 4048-4053CODEN: PCOHC2; ISSN:1759-9962. (Royal Society of Chemistry)
      Novel conjugated polymers based on 3,6-carbazole repeat units were synthesized by nickel-catalyzed Yamamoto coupling under microwave heating. The resulting poly(3,6-carbazole)s contain tetraphenylethylene (TPE) units in their side chains. The resultant polymers show aggregation induced emission (AIE) behavior. Hereby, the photoluminescence (PL) intensity of PCzTPE0.5 in 90% water-THF is 35 times higher than that in pure THF, connected to the introduction of TPE side chains. The ability of polymer PCzTPE0.5 for explosive sensing was also studied. A max. Stern-Volmer quenching const. of 1.26 × 106 M-1 was obsd. for PL quenching of PCzTPE0.5 aggregates by trinitrobenzene (TNB). A solid state paper strip test based on PCzTPE0.5 and PCzTPE also demonstrates effective PL quenching towards both TNB vapor and soln.
    55. 55
      Hong, Y.; Lam, J. W. Y.; Tang, B. Z. Aggregation-Induced Emission. Chem. Soc. Rev. 2011, 40, 5361– 5388,  DOI: 10.1039/c1cs15113d
      55
      Aggregation-induced emission
      Hong, Yuning; Lam, Jacky W. Y.; Tang, Ben Zhong
      Chemical Society Reviews (2011), 40 (11), 5361-5388CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Luminogenic materials with aggregation-induced emission (AIE) attributes have attracted much interest since the debut of the AIE concept in 2001. In this crit. review, recent progress in the area of AIE research is summarized. Typical examples of AIE systems are discussed, from which their structure-property relationships are derived. Through mechanistic decipherment of the photophys. processes, structural design strategies for generating new AIE luminogens are developed. Technol., esp. optoelectronic and biol., applications of the AIE systems are exemplified to illustrate how the novel AIE effect can be utilized for high-tech innovations (183 refs.).
    56. 56
      Palma-Cando, A.; Woitassek, D.; Brunklaus, G.; Scherf, U. Luminescent Tetraphenylethene-Cored, Carbazole- and Thiophene-Based Microporous Polymer Films for the Chemosensing of Nitroaromatic Analytes. Mater. Chem. Front. 2017, 1, 1118– 1124,  DOI: 10.1039/C6QM00281A
      56
      Luminescent tetraphenylethene-cored, carbazole- and thiophene-based microporous polymer films for the chemosensing of nitroaromatic analytes
      Palma-Cando, A.; Woitassek, D.; Brunklaus, G.; Scherf, U.
      Materials Chemistry Frontiers (2017), 1 (6), 1118-1124CODEN: MCFAC5; ISSN:2052-1537. (Royal Society of Chemistry)
      A series of novel microporous polymer networks (MPNs) have been prepd. from tetraphenylethene (TPE)-cored, multifunctional carbazole- or thiophene-based monomers by using chem. and electrochem. oxidative coupling methods. Octafunctional monomers lead to MPNs with a high degree of crosslinking and optimized sp. surface areas (SBET) of up to 2200 m2 g-1. Aggregation-induced emission (AIE) activity of the monomers is demonstrated. The MPN films are tested for application in the chem. sensing of nitroarom. analytes by fluorescence quenching.
    57. 57
      Gu, C.; Huang, N.; Wu, Y.; Xu, H.; Jiang, D. Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity. Angew. Chem., Int. Ed. 2015, 54, 11540– 11544,  DOI: 10.1002/anie.201504786
      57
      Design of Highly Photofunctional Porous Polymer Films with Controlled Thickness and Prominent Microporosity
      Gu, Cheng; Huang, Ning; Wu, Yang; Xu, Hong; Jiang, Donglin
      Angewandte Chemie, International Edition (2015), 54 (39), 11540-11544CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Porous org. polymers allow the integration of various π-units into robust porous π-networks, but they are usually synthesized as unprocessable solids with poor light-emitting performance as a result of aggregation-related excitation dissipation. Herein, we report a general strategy for the synthesis of highly emissive photofunctional porous polymer films on the basis of a complementary scheme for the structural design of aggregation-induced-emissive π-systems. We developed a high-throughput and facile method for the direct synthesis of large-area porous thin films at the liq.-electrode interface. The approach enables the prepn. of microporous films within only a few seconds or minutes and allows precise control over their thickness with sub-nanometer precision. By virtue of rapid photoinduced electron transfer, the thin films can detect explosives with enhanced sensitivity to low parts-per-million levels in a selective manner.
    58. 58
      Shaw, P. E.; Burn, P. L. Real-Time Fluorescence Quenching-Based Detection of Nitro-Containing Explosive Vapours: What are the Key Processes?. Phys. Chem. Chem. Phys. 2017, 19, 29714– 29730,  DOI: 10.1039/C7CP04602B
      58
      Real-time fluorescence quenching-based detection of nitro-containing explosive vapors: what are the key processes?
      Shaw, P. E.; Burn, P. L.
      Physical Chemistry Chemical Physics (2017), 19 (44), 29714-29730CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      A review. The detection of explosives continues to be a pressing global challenge with many potential technologies being pursued by the scientific research community. Luminescence-based detection of explosive vapors with an org. semiconductor has attracted much interest because of its potential for detectors that have high sensitivity, compact form factor, simple operation and low-cost. Despite the abundance of literature on novel sensor materials systems there are relatively few mechanistic studies targeted towards vapor-based sensing. In this perspective, the progress is reviewed that has been made in understanding the processes that control the real-time luminescence quenching of thin films by analyte vapors. These are the non-radiative quenching processes by which the sensor exciton decays, the analyte-sensor intermol. binding interaction, and the diffusion process for the analyte vapors in the film. The contributions are commented of each of these processes towards the sensing response and, in particular, the relative roles of analyte diffusion and exciton diffusion. While the latter has been historically judged to be one of, if not the primary, causes for the high sensitivity of many conjugated polymers to nitrated vapors, recent evidence suggests that long exciton diffusion lengths are unnecessary. The implications of these results on the development of sensor materials for real-time detection are discussed.
    59. 59
      Räupke, A.; Palma-Cando, A.; Shkura, E.; Teckhausen, P.; Polywka, A.; Görrn, P.; Scherf, U.; Riedl, T. Highly Sensitive Gas-Phase Explosive Detection by Luminescent Microporous Polymer Networks. Sci. Rep. 2016, 6, 29118,  DOI: 10.1038/srep29118
      59
      Highly sensitive gas-phase explosive detection by luminescent microporous polymer networks
      Raupke Andre; Shkura Eugen; Riedl Thomas; Palma-Cando Alex; Scherf Ullrich; Teckhausen Peter; Polywka Andreas; Gorrn Patrick
      Scientific reports (2016), 6 (), 29118 ISSN:.
      We propose microporous networks (MPNs) of a light emitting spiro-carbazole based polymer (PSpCz) as luminescent sensor for nitro-aromatic compounds. The MPNs used in this study can be easily synthesized on arbitrarily sized/shaped substrates by simple and low-cost electrochemical deposition. The resulting MPN afford an extremely high specific surface area of 1300 m(2)/g, more than three orders of magnitude higher than that of the thin films of the respective monomer. We demonstrate, that the luminescence of PSpCz is selectively quenched by nitro-aromatic analytes, e.g. nitrobenzene, 2,4-DNT and TNT. In striking contrast to a control sample based on non-porous spiro-carbazole, which does not show any luminescence quenching upon exposure to TNT at levels of 3 ppm and below, the microporous PSpCz shows a clearly detectable response even at TNT concentrations as low as 5 ppb, clearly demonstrating the advantage of microporous films as luminescent sensors for traces of explosive analytes. This level states the vapor pressure of TNT at room temperature.
    60. 60
      Gu, C.; Huang, N.; Gao, J.; Xu, F.; Xu, Y.; Jiang, D. Controlled Synthesis of Conjugated Microporous Polymer Films: Versatile Platforms for Highly Sensitive and Label-Free Chemo- and Biosensing. Angew. Chem., Int. Ed. 2014, 53, 4850– 4855,  DOI: 10.1002/anie.201402141
      60
      Controlled Synthesis of Conjugated Microporous Polymer Films: Versatile Platforms for Highly Sensitive and Label-Free Chemo- and Biosensing
      Gu, Cheng; Huang, Ning; Gao, Jia; Xu, Fei; Xu, Yanhong; Jiang, Donglin
      Angewandte Chemie, International Edition (2014), 53 (19), 4850-4855CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Conjugated microporous polymers (CMPs), in which rigid building blocks form robust networks, are usually synthesized as insol. and unprocessable powders. The authors developed a methodol. using electropolymn. for the synthesis of thin CMP films. The thickness of these films is synthetically controllable, ranging from nanometers to micrometers, and they are obtained on substrates or as freestanding films. The CMP films combine a no. of striking phys. properties, including high porosity, extended π conjugation, facilitated exciton delocalization, and high-rate electron transfer. The authors explored the CMP films as versatile platforms for highly sensitive and label-free chemo- and biosensing of electron-rich and electron-poor arenes, metal ions, dopamine, and hypochloric acid, featuring rapid response, excellent selectivity, and robust reusability.
    61. 61
      Liu, H.; Liu, H. Selective Dye Adsorption and Metal Ion Detection Using Multifunctional Silsesquioxane-Based Tetraphenylethene-Linked Nanoporous Polymers. J. Mater. Chem. A 2017, 5, 9156– 9162,  DOI: 10.1039/C7TA01255A
      61
      Selective dye adsorption and metal ion detection using multifunctional silsesquioxane-based tetraphenylethene-linked nanoporous polymers
      Liu, Huanhuan; Liu, Hongzhi
      Journal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (19), 9156-9162CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)
      Multifunctional hybrid fluorescent porous materials have been prepd. by the Friedel-Crafts reaction of octavinylsilsesquioxane (OVS) with tetraphenylethene (TPE). These hybrid porous polymers possess high surface areas of up to 1910 cm2 g-1, and bimodal pore structures with micropores centered at ≈1.4 nm and mesopores centered at ≈4.5 nm. They show a moderate CO2 adsorption capacity of 6.25 wt% (1.42 mmol g-1) at 273 K/101 kPa. Remarkably, they exhibit highly size-selective adsorption of dye of 1666 mg g-1 for rhodamine B (RB), 1040 mg g-1 for congo red (CR) and 862 mg g-1 for crystal violet (CV). Furthermore, the incorporation of a tetraphenylethene unit induces higher fluorescence (λem = 490 nm) and high sensitivity for Fe3+, Cu2+ and Ru3+, esp. for Fe3+ with KSV = 140 K M-1. They are very promising for multiple applications in dye sepn., sensors, etc.
    62. 62
      Gopalakrishnan, D.; Dichtel, W. R. Real-Time, Ultrasensitive Detection of RDX Vapors Using Conjugated Network Polymer Thin Films. Chem. Mater. 2015, 27, 3813– 3816,  DOI: 10.1021/acs.chemmater.5b00857
      62
      Real-Time, Ultrasensitive Detection of RDX Vapors Using Conjugated Network Polymer Thin Films
      Gopalakrishnan, Deepti; Dichtel, William R.
      Chemistry of Materials (2015), 27 (11), 3813-3816CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      1,3,5-Trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) are primary components in improvised explosive devices (IEDs), but detection of these explosives in air is challenging because of their low volatility. Here the authors report the synthesis of tris(phenylene)vinylene (TPV) polymer thin films that are chem. bonded to fused SiO2 substrates bearing allyl siloxane monolayers. This procedure provides previously unavailable control over the TPV film's thickness, a crit. parameter for trace explosives detection. TPV film growth was optimized to detect RDX from the vapor phase in as little as 10 s, as well as attograms of HMX that was introduced from soln. These results suggest a balance between film thickness and the extent of the olefin metathesis reaction that influence the polymer's sensing performance. The sensitivity of TPV fluorescence to nitramine explosives is of interest for aviation and military security.
    63. 63
      Preis, E.; Widling, C.; Brunklaus, G.; Schmidt, J.; Thomas, A.; Scherf, U. Microporous Polymer Networks (MPNs) Made in Metal-Free Regimes: Systematic Optimization of a Synthetic Protocol toward N -Arylcarbazole-Based MPNs. ACS Macro Lett. 2013, 2, 380– 383,  DOI: 10.1021/mz400126f
      63
      Microporous Polymer Networks (MPNs) Made in Metal-Free Regimes: Systematic Optimization of a Synthetic Protocol toward N-Arylcarbazole-Based MPNs
      Preis, Eduard; Widling, Christian; Brunklaus, Gunther; Schmidt, Johannes; Thomas, Arne; Scherf, Ullrich
      ACS Macro Letters (2013), 2 (5), 380-383CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      Acidic self-condensation of 2,7-bis(N-carbazolyl)-9-fluorenone produces microporous polymer networks (MPNs) with high Brunauer-Emmett-Teller (BET) surface areas of up to 2250 m2/g and hydrogen storage capacities of up to 1.7% (at 1 bar) in a fully metal-free condensation regime.
    64. 64
      Pauporté, T.; Rathouský, J. Electrodeposited Mesoporous ZnO Thin Films as Efficient Photocatalysts for the Degradation of Dye Pollutants. J. Phys. Chem. C 2007, 111, 7639– 7644,  DOI: 10.1021/jp071465f
      64
      Electrodeposited Mesoporous ZnO Thin Films as Efficient Photocatalysts for the Degradation of Dye Pollutants
      Pauporte, T.; Rathousky, J.
      Journal of Physical Chemistry C (2007), 111 (21), 7639-7644CODEN: JPCCCK; ISSN:1932-7447. (American Chemical Society)
      Thin, meso-porous ZnO films were prepd. by electrochem. deposition using eosin Y as a structure-directing agent. After removing the eosin from the structure, transparent porous ZnO films were obtained. Film porosity and surface area were detd. by performing krypton BET measurements. Electrochem. deposition parameters (deposition time and plating bath eosin concn.) were optimized to prep. films with large internal surface areas and good mech. properties. Eosin concns. of 50-60 μM gave the best quality meso-porous ZnO with film thicknesses of 2-3 μm. Photodegrdn. of a hetero-polyarom. (methylene blue) and diazo dyes (congo red) served as model reactions to assess ZnO film photocatalytic activity. For both dyes, the photodegrdn. rate reached its max. for meso-porous films prepd. with eosin concns. >40 μM. Since photodegrdn. occurred preferentially in the larger-diam. film pores, development of a very large surface area due to a fine network of meso-pores narrower than 8 nm did not significantly enhance photocatalytic performance of ZnO films.
    65. 65
      Jeromenok, J.; Weber, J. Restricted Access: On the Nature of Adsorption/Desorption Hysteresis in Amorphous, Microporous Polymeric Materials. Langmuir 2013, 29, 12982– 12989,  DOI: 10.1021/la402630s
      65
      Restricted Access: On the Nature of Adsorption/Desorption Hysteresis in Amorphous, Microporous Polymeric Materials
      Jeromenok, Jekaterina; Weber, Jens
      Langmuir (2013), 29 (42), 12982-12989CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      The phenomenon of low-pressure adsorption/desorption hysteresis, which is commonly obsd. in microporous polymers, is investigated by detailed gas adsorption studies. Diffusional limitations by pore blocking effects, which arise as a consequence of the micropore morphol. and connectivity, are discussed as the origin of the hysteresis rather than swelling effects, which have been suggested previously. Micropores with narrow openings, which cannot be filled easily, are expected to be present next to open pores. Those pores are termed restricted-access pores and are only filled in the course of the adsorption process as a consequence of the increasing solvation pressure exhibited from already filled micropores. As a consequence of the results presented here, it is suggested to use the desorption branch in addn. to the adsorption branch for the extn. of the porosity characteristics, such as sp. surface area, pore vol., and pore size distribution. The magnitude of the low-pressure hysteresis might hence give an idea of the micropore connectivity, which is important information for potential applications.
    66. 66
      Kulkarni, A. P.; Kong, X.; Jenekhe, S. A. Polyfluorene Terpolymers Containing Phenothiazine and Fluorenone: Effects of Donor and Acceptor Moieties on Energy and Intrachain Charge Transfer Processes in the Photoluminescence and Electroluminescence of Multichromophore Copolymers. Macromolecules 2006, 39, 8699– 8711,  DOI: 10.1021/ma0617062
      There is no corresponding record for this reference.
    67. 67
      Schneider, D.; Mehlhorn, D.; Zeigermann, P.; Kärger, J.; Valiullin, R. Transport Properties of Hierarchical Micro-Mesoporous Materials. Chem. Soc. Rev. 2016, 45, 3439– 3467,  DOI: 10.1039/C5CS00715A
      67
      Transport properties of hierarchical micro-mesoporous materials
      Schneider, Daniel; Mehlhorn, Dirk; Zeigermann, Philipp; Kaerger, Joerg; Valiullin, Rustem
      Chemical Society Reviews (2016), 45 (12), 3439-3467CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      Adding mesopore networks in microporous materials using the principles of hierarchical structure design is recognized as a promising route for eliminating their transport limitations and, therefore, for improving their value in technol. applications. Depending on the routes of physico-chem. procedures or post-synthesis treatments used, very different geometries of the intentionally-added transport mesopores can be obtained. Understanding the structure-dynamics relationships in these complex materials with multiple porosities under different thermodynamical conditions remains a challenging task. In this review, we summarize the results obtained so far on exptl. and theor. studies of diffusion in micro-mesoporous materials. By considering four common classes of bi-porous materials, which are differing by the inter-connectivities of their sup-spaces as one of the most important parameter detg. the transport rates, we discuss their generic transport properties and correlate the results delivered by the equil. and non-equil. techniques of diffusion measurements.
    68. 68
      Hu, Z.; Deibert, B. J.; Li, J. Luminescent Metal-Organic Frameworks for Chemical Sensing and Explosive Detection. Chem. Soc. Rev. 2014, 43, 5815– 5840,  DOI: 10.1039/C4CS00010B
      68
      Luminescent metal-organic frameworks for chemical sensing and explosive detection
      Hu, Zhichao; Deibert, Benjamin J.; Li, Jing
      Chemical Society Reviews (2014), 43 (16), 5815-5840CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Metal-org. frameworks (MOFs) are a unique class of cryst. solids comprised of metal cations (or metal clusters) and org. ligands that have shown promise for a wide variety of applications. Over the past 15 years, research and development of these materials have become one of the most intensely and extensively pursued areas. A very interesting and well-investigated topic is their optical emission properties and related applications. Several reviews have provided a comprehensive overview covering many aspects of the subject up to 2011. This review intends to provide an update of work published since then and focuses on the photoluminescence (PL) properties of MOFs and their possible utility in chem. and biol. sensing and detection. The spectrum of this review includes the origin of luminescence in MOFs, the advantages of luminescent MOF (LMOF) based sensors, general strategies in designing sensory materials, and examples of various applications in sensing and detection.
    69. 69
      Kumar, M.; Vij, V.; Bhalla, V. Vapor-Phase Detection of Trinitrotoluene by AIEE-Active Hetero-Oligophenylene-Based Carbazole Derivatives. Langmuir 2012, 28, 12417– 12421,  DOI: 10.1021/la302309z
      69
      Vapor-Phase Detection of Trinitrotoluene by AIEE-Active Hetero-oligophenylene-Based Carbazole Derivatives
      Kumar, Manoj; Vij, Varun; Bhalla, Vandana
      Langmuir (2012), 28 (33), 12417-12421CODEN: LANGD5; ISSN:0743-7463. (American Chemical Society)
      New AIEE-active hetero-oligophenylene carbazole derivs. 3 and 4 were synthesized and serve as fluorescent probes for the selective detection of 2,4,6-trinitrotoluene (TNT) in the vapor phase, the solid phase, and aq. media. Paper strips prepd. by dip-coating a soln. of aggregates of derivs. 3 and 4 can provide a simple, portable, sensitive, selective, low-cost method for the detection of TNT on the picogram level.
    70. 70
      Nie, H.; Zhao, Y.; Zhang, M.; Ma, Y.; Baumgarten, M.; Müllen, K. Detection of TNT Explosives with a New Fluorescent Conjugated Polycarbazole Polymer. Chem. Commun. (Cambridge, U. K.) 2011, 47, 1234– 1236,  DOI: 10.1039/C0CC03659E
      70
      Detection of TNT explosives with a new fluorescent conjugated polycarbazole polymer
      Nie, Heran; Zhao, Yang; Zhang, Ming; Ma, Yuguang; Baumgarten, Martin; Muellen, Klaus
      Chemical Communications (Cambridge, United Kingdom) (2011), 47 (4), 1234-1236CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A novel fluorescent poly(2,7-carbazole) with a 4-[tris-(4-octyloxyphenyl)methyl]phenyl side chain is used to detect the explosive compds. TNT and DNT. It shows high recycled fluorescence quenching sensitivity, which is due to its strong electron donating ability and weaker interaction between the polymer chains caused by the bulky side chain.
    71. 71
      Naddo, T.; Che, Y.; Zhang, W.; Balakrishnan, K.; Yang, X.; Yen, M.; Zhao, J.; Moore, J. S.; Zang, L. Detection of Explosives with A Fluorescent Nanofibril Film. J. Am. Chem. Soc. 2007, 129, 6978– 6979,  DOI: 10.1021/ja070747q
      71
      Detection of Explosives with a Fluorescent Nanofibril Film
      Naddo, Tammene; Che, Yanke; Zhang, Wei; Balakrishnan, Kaushik; Yang, Xiaomei; Yen, Max; Zhao, Jincai; Moore, Jeffrey S.; Zang, Ling
      Journal of the American Chemical Society (2007), 129 (22), 6978-6979CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      A new type of fluorescence sensory material was developed from an alkoxycarbonyl-substituted carbazole-cornered tetracycle. Films fabricated from such materials are shown to be efficient in detecting explosive vapor, probably owing to the extended 1D mol. stacking between the component mols. and intrinsic nanoporous morphol. thus formed within the film. The former facilitates long-range exciton migration, while the latter favors adsorption and diffusion of gaseous adsorbates within the film. A combination of these two characteristics enables efficient fluorescence quenching of the film by gaseous quenchers.
    72. 72
      Xu, B.; Wu, X.; Li, H.; Tong, H.; Wang, L. Selective Detection of TNT and Picric Acid by Conjugated Polymer Film Sensors with Donor–Acceptor Architecture. Macromolecules 2011, 44, 5089– 5092,  DOI: 10.1021/ma201003f
      72
      Selective Detection of TNT and Picric Acid by Conjugated Polymer Film Sensors with Donor-Acceptor Architecture
      Xu, Bowei; Wu, Xiaofu; Li, Haibo; Tong, Hui; Wang, Lixiang
      Macromolecules (Washington, DC, United States) (2011), 44 (13), 5089-5092CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      A strong donor-acceptor polymer P1 and two donor-only polymers P2 and P3 are designed and synthesized on the basis of the rational anal. of the electrostatic potential and the LUMO distribution for highly selective and sensitive detection of TNT and picric acid in aq. solns., resp. Although their emission in soln. states is very poor, spin-coating films of these AIE-active polymers exhibit bright emission. For the P1 film, the Stern-Volmer quenching const., Ksv of TNT (1.2 ×. 105 M-1) is almost 2 orders higher than that of picric acid (1.8 × 103 M-1), and the detection limit of TNT is about 23 ppb, while the emission of the P3 film can be selectively quenched by the picric acid with the Ksv const. 2.8 × 104 M-1 and the detection limit 2 ppb. These quenching effects of both TNT and picric acid on the P1 and P3 films are found to be reversible. In addn., it was also demonstrated that the emission of P1 and P3 films could be efficiently quenched by TNT and DNT vapors.

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    • Synthetic procedure of monomer and bulk polymers, CV of polymers in monomer-free solution, FTIR spectra, solid-state NMR spectra, TGA, absorption and emission spectra of polymer films, ultraviolet photoemission spectra of polymer films, polymer energy-level diagram (PDF)


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