Thermodynamics and Kinetics of CO2 Adsorption on Dehydrated Palladium/Cobalt-Based Cyanogels:  A Highly Selective, Fully Reversible System for CO2 Storage

Carbon dioxide is selectively adsorbed on cyanide-bridged palladium/cobalt gels, synthesized from aqueous solutions of Na2PdCl4 and K3[Co(CN)6]. The cyanide bridges, connecting the palladium and cobalt metal centers, are characteristic of these gels; hence, these gels are termed cyanogels. The thermodynamics and kinetics of the CO2 adsorption and desorption processes on aerogels and xerogels formed from Pd/Co cyanogels are analyzed here. Aerogel versus xerogel structures have a profound effect on the thermodynamics and kinetics of CO2 adsorption. The CO2 adsorption process is fully reversible on both types of gels discussed. The gas adsorption capacity of the aerogel exceeds that of the xerogel by a factor of slightly over two. From the ease and reproducibility of the CO2 desorption and the associated enthalpy values, it is concluded that CO2 is physisorbed on these gels. The kinetics of adsorption and desorption are analyzed: both processes are first-order in the gels.