Extraordinary Separation of Acetylene-Containing Mixtures in a Honeycomb Calcium-Based MOF with Multiple Active Sites.

Acetylene (C 2 H 2 ) separation from multicomponent mixtures is vitally important but industrially challenging for the collection of high-purity C 2 H 2 . To address this requirement, the reaction between the alkaline-earth Ca 2+ ions with a dicarboxylate-diazolate linker, 4,6-di(1 H -tetrazol-5-yl)isophthalic acid (H 4 dtzip), gave rise to a new metal-organic framework (MOF) material [Ca(dtzip) 0.5 H 2 O]·2H 2 O ( 1 ). The material presents unique regular tubular channels based on threefolded helical rod-like secondary building units with rich open metal sites and exposed organic hydrogen-bonding N/O acceptors that enhance the interactions with C 2 H 2 molecules, endowing significant selectivity for C 2 H 2 over C 2 H 4 (5.4), C 2 H 6 (5.6), CH 4 (30.0), and CO 2 (7.7) at 298 K and 100 kPa. Column breakthrough experiments confirmed the extraordinary C 2 H 2 separation performance of the material with the separation time intervals in the range of 18-24 min g -1 for binary (C 2 H 2 -C 2 H 4 , C 2 H 2 -C 2 H 6 , C 2 H 2 -CO 2 , and C 2 H 2 -CH 4 ) or ternary (C 2 H 2 -C 2 H 4 -C 2 H 6 and C 2 H 2 -C 2 H 4 -CO 2 ) gas mixtures under dynamic conditions.