The effect of pore size dimensions in isoreticular zeolites on carbon dioxide adsorption heats

Adsorption isotherms of carbon dioxide were measured on a family of IPC-2, IPC-4, IPC-6, and IPC-7 siliceous isoreticular zeolites prepared from UTL germanosilicate. New strategy called ADOR allowed to synthesize isoreticular materials having the same structure of individual layers but gradually reduced channel size of 9.5 x 7.1 (14-ring), 8.5 x 5.5 (12-ring), 6.6 x 6.2 (12-ring), 5.4 x 5.3 (10-ring) and 4.5 x 3.6 (8-ring) angstrom. These IPC-n zeolites present an excellent set of siliceous model materials to analyze the effect of micropore structure on adsorption of carbon dioxide. Isosteric adsorption heats of carbon dioxide were determined from adsorption isotherms measured in the range 273 K-333 K up to 101 kPa. Obtained dependences of the adsorption heat of CO2 on the amount adsorbed are more sensitive to the adsorbent structure than single adsorption isotherms. It appears that due to domination of dispersion interactions of carbon dioxide with zeolites under study isosteric adsorption heat characterizes the structure features of investigated zeolites with a higher resolution then adsorption isotherms.