A comparison of the H-2 sorption capacities of isostructural metal-organic frameworks with and without accessible metal sites: [{Zn-2(abtc)(dMf)(2)}(3)] and [{Cu-2(abtc)(dMf)(2)}(3)] versus [{Cu-2(abtc)}(3)]

Abstract

The isostructural metal-organic frameworks [{Zn2(abtc)(dmf) 2}3] (1a), [{Cu2(abtc)(dmf)2} 3] (2a), and [{Cu2(abtc)}3] (2b; H 4abtc = 1,1′-azobenzene-3,3′,5,5′-tetracarboxylic acid) have high sorption capacities for H2, N2, CO 2, and CH4. Solid 2b, which has accessible metal sites (AMSs), has a higher H2 adsorption capacity than 1a or 2a (see picture; T = 77 K), neither of which have AMSs, because of its lower molecular weight and greater isosteric heat of H2 adsorption.