title: Molecular basis for the high CO2 adsorption capacity of chabazite zeolites.
abstract: CO2 adsorption in Li-, Na-, K-CHA (Si/Al=6,=12), and silica chabazite zeolites was investigated by powder diffraction. Two CO2 adsorption sites were found in all chabazites with CO2 locating in the 8-membered ring (8MR) pore opening being the dominant site. Electric quadrupole-electric field gradient and dispersion interactions drive CO2 adsorption at the middle of the 8 MRs, while CO2 polarization due to interaction with cation sites controls the secondary CO2 site. In Si-CHA, adsorption is dominated by dispersion interactions with CO2 observed on the pore walls and in 8 MRs. CO2 adsorption complexes on dual cation sites were observed on K-CHA, important for K-CHA-6 samples due to a higher probability of two K(+) cations bridging CO2. Trends in isosteric heats of CO2 adsorption based on cation type and concentration can be correlated with adsorption sites and CO2 quantity. A decrease in the hardness of metal cations results in a decrease in the direct interaction of these cations with CO2.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Center for Catalytic Science and Technology, University of Delaware, 150 Academy St., Newark, Delaware 19716 (USA).
authors.forename: Trong D
authors.initials: TD
authors.lastname: Pham
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Hudson
authors.forename: Craig M
authors.initials: CM
authors.lastname: Brown
authors.forename: Raul F
authors.initials: RF
authors.lastname: Lobo
mesh_terms: D000327:Adsorption; D002245:Carbon Dioxide / Q000737:chemistry*; D007474:Ion Exchange; D008094:Lithium / Q000737:chemistry; D011188:Potassium / Q000737:chemistry; D033362:Powder Diffraction; D012964:Sodium / Q000737:chemistry; D013329:Structure-Activity Relationship; D017641:Zeolites / Q000737:chemistry*
chemical_list: C554923:chabazite; D017641:Zeolites; D002245:Carbon Dioxide; D008094:Lithium; D012964:Sodium; D011188:Potassium
keywords: X-ray diffraction; carbon dioxide adsorption; chabazite; neutron diffraction; zeolites