Substituent Engineering-Enabled Structural Rigidification and Performance Improvement for C/CO Separation in Three Isoreticular Coordination Frameworks.

Construction of porous solid materials applied to the adsorptive removal of CO from C hydrocarbons is highly demanded thanks to the important role C hydrocarbons play in the chemical industry but quite challenging owing to the similar physical parameters between C hydrocarbons and CO. In particular, the development of synthetic strategies to simultaneously enhance the uptake capacity and adsorption selectivity is very difficult due to the trade-off effect frequently existing between both of them. In this work, a combination of the dicopper paddlewheel unit and 4-pyridylisophthalate derivatives bearing different substituents afforded an isoreticular family of coordination framework compounds as a platform. Their adsorption properties toward C hydrocarbons and CO were systematically investigated, and subsequent IAST and density functional theory calculations combined with column breakthrough experiments verified their promising potential for C/CO separations. Furthermore, the substituent engineering endowed the resulting compounds with simultaneous enhancement of uptake capacity and adsorption selectivity and thus better C/CO separation performance compared to their parent compound. The substituent introduction not only mitigated the framework distortion via fixing the ligand conformation for establishment of better permanent porosity required for gas adsorption but also polarized the framework surface for host-guest interaction improvement, thus resulting in enhanced separation performance.