Carbon dioxide storage and sustained delivery by Cu2(pzdc)2L [L = dipyridyl-based ligand] pillared-layer porous coordination networks

CPL-2 (Cu-2(pzdc)(2)(bpy)), CPL-5 ((Cu-2(pzdc)(2)(bpe)), and ZIF-8 (Zn(MelM)(2)) [pzdc = 2,3-pyrazinedicarboxylate, bpy = 4,4'bipyridine, bpe = 1,2-di-(4-pyridyl)-ethylene, MeIM = 2-methylimidazolate] were used to study carbon dioxide storage and delivery at low to moderate pressures. Both CPL-2 and CPL-5 showed superior performance over ZIF-8 due to better volumetric-based capacities and superior diffusion kinetics exhibited by the former metal organic frameworks. When compared with an empty vessel, the CPL-n based storage/delivery system provided as much as 500% increase in CO2 constant flow supply time at moderate pressures. A simplified phenomenological yet useful model was developed to predict discharge pressure decay and estimate a lumped parameter related to the molecular diffusivity. Density functional theory was also employed to shed light onto the CO2 hysteretic adsorption process present on the CPL-n materials. Greater CO2 binding interactions were observed near the vicinity of the copper-nodes. (C) 2013 Elsevier Inc. All rights reserved.