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

Abstract

Four new layered flexible metal–organic frameworks (MOFs) containing a diacylhydrazone moiety, namely, guest-filled [Zn 2 (iso) 2 (tdih) 2 ] n ( 1 ), [Zn 2 (NH 2 iso) 2 (tdih) 2 ] n ( 2 ), [Cd 2 (iso) 2 (tdih) 2 ] n ( 3 ) and [Cd 2 (NH 2 iso) 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 (NH 2 iso) 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 CO 2 adsorption. Gently activated aminoisophthalate-based frameworks, that is, guest-exchanged in methanol and heated to 100 °C, show reversible gated CO 2 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.

Structural transitions during the water sorption process in two layered metal hydrogen-bonded organic frameworks and the effect of the H-bond strength between the layers

“…31 This interpretation is in agreement with the results obtained by Roztocki et al in the study of the CO 2 sorption on 2D isophthalic- and 5-aminoisophthalic-MOFs. 34 Actually, sigmoidal isotherms were observed for MOFs having amino-substituted linkers, while no steps were observed for MOFs with unsubstituted linkers.…”

“…To the best of our knowledge, to date this effect was only reported by Roztocki et al for CO 2 sorption on the 2D isophthalic- and 5-aminoisophthalic-MOFs, and infrared analyses with an assumption on the structure of activated materials (not obtained) were used for elucidation. 34 In situ powder X-ray diffraction (PXRD) measurements were used in this work.…”

Two-Dimensional Metal-Organic Framework Materials: Synthesis, Structures, Properties and Applications

“…The sorption properties of this MOF has been modified by changing the size, shape, and dimensionality of the nanocrystals by using inverse micro-emulsion (oil in water) technique . Very recently, four interdigitated 2D MOFs, [Zn 2 ­(ip) 2 ­(tdih) 2 ], [Zn 2 ­(NH 2 ip) 2 ­(tdih) 2 ], [Cd 2 ­(ip) 2 ­(tdih) 2 ], and [Cd 2 ­(NH 2 ip) 2 ­(tdih) 2 ] (tdih = terephthalaldehyde di-isonicotinoylhydrazone), have been also reported in which amino-based frameworks displayed reversible gated CO 2 adsorption at 195 K with higher uptake capacity compared to without amino-substituted ones …”

“…794 Very recently, four interdigitated 2D MOFs, [Zn 2 (ip) 2 (tdih) 2 ], [Zn 2 (NH 2 ip) 2 -(tdih) 2 ], [Cd 2 (ip) 2 (tdih) 2 ], and [Cd 2 (NH 2 ip) 2 (tdih) 2 ] (tdih = terephthalaldehyde di-isonicotinoylhydrazone), have been also reported in which amino-based frameworks displayed reversible gated CO 2 adsorption at 195 K with higher uptake capacity compared to without amino-substituted ones. 795 Another flexible layer structure, [Cd(bpndc)(bpy)] (bpndc = benzophenone-4,4′-dicarboxylate), show a large difference in gate-opening pressure between O 2 , Ar, and N 2 (Figure 167). 796 The gate-opening characteristics have been quantified as O 2 > N 2 > Ar, which is very similar to the boiling point of the respective gases.…”

Synthesis, structure and magnetocaloric properties of a new two-dimensional gadolinium(III) coordination polymer based on azobenzene-2,2′,3,3′-tetracarboxylic acid

“…Coordination polymers (CPs), a class of compounds based on repetition of metal cations connected by coordinated linkers, have developed rapidly in the past 20 years (Chakraborty et al, 2021) due to their interesting structures and variable applications in gas storage and separation (Roztocki et al, 2020), catalysis (Kang et al, 2019), sensing (Lustig et al, 2017) and magnetic materials (Yang et al, 2019a). In particular, due to the unique 4f electron configuration of Ln 3+ ions, lanthanide coordination polymers (Ln-CPs) usually exhibit a high coordination number, flexible coordination geometry and strong spin-orbit coupling (Sorace et al, 2011;Liu et al, 2016).…”