Experimental and computational study of functionality impact on sodalite-zeolitic imidazolate frameworks for CO2 separation

This study deals with the enhancement of CO2 uptake by ligand functionalization of zeolitic imidazolate framework (ZIF) materials. The ligand dipole moment could be considered as one of the main criteria for CO2 adsorption enhancement. To verify this hypothesis, an experimental- computational study was performed on an isoreticular ZIF series with sodalite (SOD) topology using published structures (ZIF-8, ZIF-90, and ZIF-Cl) as well as hypothetical structures (ZIF-COOH and ZIF-NO2) designated using DFT calculations. An analysis of structural and adsorptive properties was proposed for these materials used to separate CO2 from CH4, CO, or N2 gas. The accuracy of the calculated results was validated by comparison with our own experimental results. An exponential relationship between the ligand dipole moments and the isosteric heat of adsorption of CO2 was highlighted. Modifying the nature of the linker (dipole moment) allows a 5- to 7-fold improvement in CO2 selectivity for CO2/CH4, CO2/N2, and CO 2/CO mixtures. © 2011 American Chemical Society.