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.

Kornel Roztocki,Monika Szufla,Stefan Kaskel,Dariusz Matoga,Volodymyr Bon,Irena Senkovska

doi:10.1021/acs.inorgchem.0c01182

Kornel Roztocki, Monika Szufla + Show 4 more

Open Access

https://doi.org/10.1021/acs.inorgchem.0c01182

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Journal: Inorganic chemistry	Publication Date: Jul 14, 2020
Citations: 15	License type: cc-by

Affiliation: Jagiellonian University, TU Dresden

Abstract

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.

Highlights

Crystalline materials that respond through structural changes to external chemical or physical stimuli, such as specific compounds,[1,2] pressure,[3] mechanical force,[4,5] electrical field,[6] or electromagnetic radiation[7] are highly desirable for smart devices and are useful for studying stimulus-structure−property relationships
We demonstrate that interlayer hydrogen bonds involving the diacylhydrazone linker have a considerable impact on porous structures as well as gas adsorption properties
Pore dimensionalities of the acylhydrazone-based metal−organic frameworks (MOFs) obtained were found to be mostly governed by different ionic radii of Zn2+ and Cd2+ ions

Summary

■ INTRODUCTION

Crystalline materials that respond through structural changes to external chemical or physical stimuli, such as specific compounds,[1,2] pressure,[3] mechanical force,[4,5] electrical field,[6] or electromagnetic radiation[7] are highly desirable for smart devices and are useful for studying stimulus-structure−. MOFs to external conditions, after local initiation, propagates through the crystalline lattice with retention of long-range order Different nanoflexibility modes such as swelling,[12] breathing,[13] linker rotation14/bending,[15] change of interpenetration level,[16] and subnetwork displacement for 3D catenated networks[17] or stacked18/interdigitated[19,20] layers drive macroscopic changes of flexible MOFs as well as govern several distinct phenomena such as gate opening,[21] negative gas adsorption,[15] pronounced usable capacity,[22] chemical control of structures,[23] continuous-breathing behavior,[24] collective breathing,[25] self-accelerating sorption,[26] shape memory effect,[27] proton conductivity,[28] and solvent-induced magnetic ordering.[29]. ■voids (Vvoids) were calculated with Mercury software by using a probe molecule with a radius of 1.2 Å (views along the a-axis)

AND DISCUSSION

■ CONCLUSION

■ ACKNOWLEDGMENTS

■ REFERENCES