Journal article

Flexible metal-organic framework compounds: In situ studies for selective CO2 capture

Results are presented that explore the dynamic structural changes occurring in two highly flexible nanocryst. metal-org. framework (MOF) compds. during the adsorption and desorption of pure gases and binary mixts. The Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)4] and catena-bis(dibenzoylmethanato)-(4,4'-bipyridyl)nickel(II) chosen for this study are 3-D and 1-D porous coordination polymers (PCP) with a similar gate opening pressure response for CO2 isotherms at 303 K, but with differing degrees of flexibility for structural change to accommodate guest mols. As such, they serve as a potential model system for evaluating the complex kinetics assocd. with dynamic structure changes occurring in response to gas adsorption in flexible MOF systems. Insights into the crystallog. changes occurring as the MOF pore structure expands and contracts in response to interactions with CO2, N2, and CO2/N2 mixts. have been obtained from in situ small-angle neutron scattering and neutron diffraction, combined with ex situ X-ray diffraction structure measurements. The role of structure in carbon capture functionality is discussed with ref. to the ongoing characterization challenges and a possible materials-by-design approach.


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