Highly Selective Separation of C₂H₂ from CO₂ by a New Dichromate-Based Hybrid Ultramicroporous Material

A new hybrid ultramicroporous material, [Ni­(1,4-di­(pyridine-2-yl)­benzene)2(Cr2O7)]n (DICRO-4-Ni-i), has been prepared and structurally characterized. Pure gas sorption isotherms and molecular modeling of sorbate–sorbent interactions imply strong selectivity for C2H2 over CO2 (SAC). Dynamic gas breakthrough coupled with temperature-programmed desorption experiments were conducted on DICRO-4-Ni-i and two other porous materials reported to exhibit high SAC, TIFSIX-2-Cu-i and MIL-100­(Fe), using a C2H2/CO2/He (10:5:85) gas mixture. Whereas CO2/C2H2 coadsorption by MIL-100­(Fe) mitigated the purity of trapped C2H2, negligible coadsorption and high SAC were observed for DICRO-4-Ni-i and TIFSIX-2-Cu-i.