Effect of Functionalized Groups on Gas-Adsorption Properties: Syntheses of Functionalized Microporous Metal-Organic Frameworks and Their High Gas-Storage Capacity

The microporous metal-organic framework (MMOF) Zn4O(L1)(2)center dot 9DMF center dot 9H(2)O (1-H) and its functionalized derivatives Zn4O(L1-CH3)(2)center dot 9DMF center dot 9H(2)O (2-CH3) and Zn4O(L1-Cl)(2)center dot 9DMF center dot 9H(2)O (3-Cl) have been synthesized and characterized (H(3)L1 = 4-[N,N-bis(4-methylbenzoicacid)amino]benzoic acid, H(3)L1-CH3 = 4-[N,N-bis(4-methylbenzoicacid)amino]-2-methylbenzoic acid, H(3)L1-Cl = 4-[N,N-bis(4-methylbenzoicacid)amino]-2-chlorobenzoic acid). Single-crystal X-ray diffraction analyses confirmed that the two functionalized MMOFs are isostructural to their parent MMOF, and are twofold interpenetrated three-dimensional (3D) microporous frameworks. All of the samples possess enduring porosity with Langmuir surface areas over 1950 cm(2) g(-1). Their pore volumes and surface areas decrease in the order 1-H>2-CH3>3-Cl. Gas-adsorption studies show that the H-2 uptakes of these samples are among the highest of the MMOFs (2.37 wt% for 3-Cl at 77 K and 1 bar), although their structures are interpenetrating. Furthermore, this work reveals that the adsorbate-adsorbent interaction plays a more important role in the gas-adsorption properties of these samples at low pressure, whereas the effects of the pore volumes and surface areas dominate the gas-adsorption properties at high pressure.