Modulation of Water Vapor Sorption by Pore Engineering in Isostructural Square Lattice Topology Coordination Networks.

We report a crystal-engineering study conducted upon a platform of three mixed-linker square lattice () coordination networks of general formula [Zn(Ria)(bphy)] [bphy = 1,2-bis(pyridin-4-yl)hydrazine, HRia = 5-position-substituted isophthalic acid, and R = -Br, -NO, and -OH; compounds -]. Analysis of single-crystal X-ray diffraction data of - and the simulated crystal structure of revealed that - are isomorphous and sustained by bilayers of networks linked by hydrogen bonds. Although similar pore shapes and sizes exist in -, distinct isotherm shapes (linear and S shape) and uptakes (2.4, 11.6, and 13.3 wt %, respectively) were observed. Ab initio calculations indicated that the distinct water sorption properties can be attributed to the R groups, which offer a range of hydrophilicity. Calculations indicated that the significantly lower experimental uptake in compound can be attributed to a constricted channel. The calculated water-binding sites provide insights into how adsorbed water molecules bond to the pore walls, with the strongest interactions, water-hydroxyl hydrogen bonding, observed for . Overall, this study reveals how pore engineering can result in large variations in water sorption properties in an isomorphous family of rigid porous coordination networks.