A Robust Molecular Porous Material for C H /CO Separation.

A molecular porous material, MPM-2, comprised of cationic [Ni (AlF )(pzH) (H O) ] and anionic [Ni Al F (pzH) (H O) ] complexes that generate a charge-assisted hydrogen-bonded network with pcu topology is reported. The packing in MPM-2 is sustained by multiple interionic hydrogen bonding interactions that afford ultramicroporous channels between dense layers of anionic units. MPM-2 is found to exhibit excellent stability in water (>1 year). Unlike most hydrogen-bonded organic frameworks which typically show poor stability in organic solvents, MPM-2 exhibited excellent stability with respect to various organic solvents for at least two days. MPM-2 is found to be permanently porous with gas sorption isotherms at 298 K revealing a strong affinity for C H over CO thanks to a high (ΔQ ) [Q (C H ) - Q (CO )] of 13.7 kJ mol at low coverage. Dynamic column breakthrough experiments on MPM-2 demonstrated the separation of C H from a 1:1 C H /CO mixture at 298 K with effluent CO purity of 99.995% and C H purity of >95% after temperature-programmed desorption. C-H···F interactions between C H molecules and F atoms of AlF are found to enable high selectivity toward C H , as determined by density functional theory simulations.