Interlinker Hydrogen Bonds Govern CO2 Adsorption in a Series of Flexible 2D Diacylhydrazone/Isophthalate-Based MOFs: Influence of Metal Center, Linker Substituent, and Activation Temperature

Four new layered flexible metal–organic frameworks (MOFs) containing a diacylhydrazone moiety, namely, guest-filled [Zn2(iso)2(tdih)2]n (1), [Zn2(NH2iso)2(tdih)2]n (2), [Cd2(iso)2(tdih)2]n (3) and [Cd2(NH2iso)2(tdih)2]n (4) were synthesized using terephthalaldehyde di-isonicotinoylhydrazone (tdih) as a linear ditopic linker as well as isophtalate (iso) or 5-aminoisophthalate (NH2iso) as angular colinkers. The MOFs with hexacoordinated cadmium centers feature two-dimensional pore systems as compared to the MOFs with pentacoordinated zinc centers showing either zero-dimensional or mixed zero-/one-dimensional voids, as evidenced by single-crystal X-ray diffraction. In contrast to the frameworks based on isophtalates which do not show any significant gas uptakes, introduction of amino-substituted linker enables CO2 adsorption. Gently activated aminoisophthalate-based frameworks, that is, guest-exchanged in methanol and heated to 100 °C, show reversible gated CO2 adsorptions at 195 K, whereas the increase of activation temperature to 150 °C or more leads to one-step isotherms and lower adsorption capacities. X-ray diffraction and IR spectroscopy reveal significant structural differences in interlayer hydrogen bonding upon activation of materials at higher temperatures. The work emphasizes the role of hydrogen bonds in crystal engineering of layered materials and the importance of activation conditions in such systems.


Table of Contents
.. 17 Figure S22 PXRD patterns for 2 after various manipulations indicated on graphs. Activation was made in low pressure (~ 10 - .. 18 Figure S23 PXRD patterns for 4 after various manipulations indicated on graphs. Activation was carried out at low pressure (~ 10 - Figure S24 Comparison of PXRD patterns for 2MeOH and 2MeOH activated in different temperatures (the patterns for activated materials were collected in inert atmosphere at RT). Small discrepancies between calculated and found PXRD pattern for 2MeOH calcd. and 2MeOH (100 o C) arise from different measurement temperature: 100 K and 298 K, respectively. .

Figure S7
Variable temperature PXRD patterns for the as-synthesized compound 1.

Figure S8
Variable temperature PXRD patterns for the as-synthesized compound 2.

Figure S9
Variable temperature PXRD patterns for the as-synthesized compound 3.

Figure S10
Variable temperature PXRD patterns for the as-synthesized compound 4.

Experimental Procedures
Diffraction intensity data for single crystals of compounds 1-4 (expect 2MeOH and 3) were collected on a KappaCCD (Nonius) diffractometer with graphite-monochromated Mo Kα radiation (λ = 0.71073 Å). A suitably sized single crystal of 2MeOH prepared in a borosilicate glass capillary (d = 0.3 mm) with small amount of the mother liquor was measured on on the Rigaku XtaLAB Synergy-S diffractometer with mirror-monochromated Mo Kα. Cell refinement and data reduction were performed using firmware. 1,2 Positions of all of non-hydrogen atoms were determined by direct methods using SIR-97. 3 All non-hydrogen atoms were refined anisotropically using weighted full-matrix least-squares on F 2 . Refinement and further calculations were carried out using SHELXL 2014/7. 4,5 All hydrogen atoms joined to carbon atoms were positioned with an idealized geometries and refined using a riding model with Uiso(H) fixed at 1.5 Ueq of C for methyl groups and 1.2 Ueq of C for other groups. The hydrogen atoms of the water (O66) molecule in 2 are indeterminate, H atoms attached to the N atoms were found in the difference-Fourier map and refined with an isotropic thermal parameter. Additionally, the crystal structure data shows that one DMF solvent molecule is heavily disordered and was removed using the SQUEEZE procedure implemented in the PLATON package. 4 In case of other two DMF solvent molecules atoms were refined using DFIX and DANG instructions. 5,6 The SQUEEZE procedure was also applied for 1 due to the presence of disordered guest molecules. The figures were made using CCDC1877585 (1), CCDC1878988 (2), CCDC1975137 (2MeOH) CCDC1898831 (3b) and CCDC1975135 (4) cif files that contain the supplementary crystallographic data.
A suitably sized single crystal of 3 was prepared in a borosilicate glass capillary (d = 0.3 mm) with small amount of the mother liquor. The dataset was collected at BESSY MX BL14.3 beamline of Helmholtz-Zentrum Berlin für Materialien und Energie. 7 Monochromatic X-ray radiation with a wavelength of λ= 0. 89500 Å (E =13.85 keV) was used in experiments. The dataset was collected at room temperature. The crystal symmetry and scan range were determined in each particular case using iMosflm program. 8 The φscans with oscillation range of 1° were used for data collection. For each dataset, 180 images were collected to reach the maximal possible completeness. The dataset was processed in automatic regime using XDSAPP 2.0 software. 9 The Crystal structures were solved by direct methods and refined by full matrix least-squares on F 2 using SHELX-2018/3 program package. 10 All non-hydrogen atoms were refined in anisotropic approximation. Hydrogen atoms were refined in geometrically calculated positions using "riding model" with Uiso(H)=1.2Uiso(C). Lattice water molecules O13-O21 were determined from the difference Fourier map and refined freely with restrains anisotropic parameters. The occupancy factor for O13, O18, O19 and O20 were refined and fixed in the last refinement cycle. The positions corresponding hydrogen atoms were determined from the electron density peaks and further refined with constrained isotropic parameter of Uiso(H)=1.2Uiso(O) and restrained geometry. The SQUEEZE procedure was applied to remove the contribution on refinement of the further lattice solvent molecules, which could not be located unambiguously 4 . CCDC1993922 contains the supplementary crystallographic data for 3 Experimental data on single crystal X-ray experiments are summarized in Table S5.
CIFs files can be obtained free of charge from the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif