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)]_<i>n</i> (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 (<i>S</i>_AC). 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 <i>S</i>_AC, 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 <i>S</i>_AC were observed for DICRO-4-Ni-i and TIFSIX-2-Cu-i