Investigation of the synthesis, activation, and isosteric heats of CO _2 adsorption of the isostructural series of metal-organic frameworks M _3(BTC) _2 (M = Cr, Fe, Ni, Cu, Mo, Ru)

摘要

The synthesis, activation, and heats of CO _2 adsorption for the known members of the M _3(BTC) _2 (HKUST-1) isostructural series (M = Cr, Fe, Ni, Zn, Ni, Cu, Mo) were investigated to gain insight into the impact of CO _2-metal interactions for CO _2 storage/separation applications. With the use of modified syntheses and activation procedures, improved BET surface areas were obtained for M = Ni, Mo, and Ru. The zero-coverage isosteric heats of CO 2 adsorption were measured for the Cu, Cr, Ni, Mo, and Ru analogues and gave values consistent with those reported for MOFs containing coordinatively unsaturated metal sites, but lower than for amine functionalized materials. Notably, the Ni and Ru congeners exhibited the highest CO _2 affinities in the studied series. These behaviors were attributed to the presence of residual guest molecules in the case of Ni _3(BTC) _2(Me _2NH) _2(H _2O) and the increased charge of the dimetal secondary building unit in [Ru _3(BTC) _2][BTC] _(0.5).