Determination of adsorption heats of individual adsorption complex by combination of microcalorimetry and FTIR spectroscopy

Adsorption of CO as a probe molecule on K-FER zeolites differing in Si/Al ratio was investigated. Successful determination of adsorption heats of individual adsorption complexes formed upon adsorption of CO molecules on K-FER zeolites at 300 K by combination of IR spectroscopy with adsorption microcalorimetry is reported. Adsorption heat of bridged carbonyl complexes, where CO molecule interacts with two nearby extraframework K⁺ cations, was experimentally determined for the first time. It was found that bridged complexes on dual cationic sites exhibit adsorption heat of 34.8 kJ mol^?1, whereas monodentate carbonyls on single isolated K⁺ cation exhibit adsorption heat of only 26.2 kJ mol^?1 and adsorption heat of isocarbonyls was 21.5 kJ mol^?1.