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 (Cr 2 O 7 )] 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 C 2 H 2 over CO 2 ( S 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 S AC, TIFSIX-2-Cu-i and MIL-100(Fe), using a C 2 H 2 /CO 2 /He (10:5:85) gas mixture. Whereas CO 2 /C 2 H 2 coadsorption by MIL-100(Fe) mitigated the purity of trapped C 2 H 2, negligible coadsorption and high S AC were observed for DICRO-4-Ni-i and TIFSIX-2-Cu-i.