Effect of Linker Substituent on Layers Arrangement, Stability, and Sorption of Zn-Isophthalate/Acylhydrazone Frameworks

A series of mixed-linker metal-organic frameworks [Zn-2(Xiso)(2)(pcih)(2)](n) containing substituted isophthalate linkers (Xiso(2-); X = OH or CH3 or NH2 or H) and 4-p-yridinecarbaldehyde isonicotinoyl hydrazone pillars (pcih) have been prepared by using both solution and mechanochemical methods. Single-crystal X-ray diffraction reveals their interdigitated two-dimensional structures with different arrangements of layers, dependent on hydrogen bonding and CH center dot center dot center dot pi interactions involving the substituents and/or linkers. These supramolecular interactions are responsible for the formation of interlayer pores of various volumes, shapes, and dimensionality. All materials exhibit selective gas adsorption of CO2 over N-2 with diverse profiles. Polar groups (OH and NH2) of the isophthalate linkers increase chemical affinity to carbon dioxide as well as hydrolytic and thermal stability of the frameworks.