Metal Node Guided Pore Engineering in Carborane-Based MOFs for Efficient C2H2/CO2 and C2H2/C2H4 Separations.

The efficient separation of C2H2 from C2H2/CO2 and C2H2/C2H4 mixtures is essential for the preparation of high-purity C2H2 and C2H4, but challenged by the trade-off between the capacity and selectivity. In this work, we report a node guided pore engineering strategy in carborane-based metal-organic frameworks (MOFs), leading to the partitioned dual cage system in Co-CB-HPBTA in contrast to its analogue Zn-CB-HPBTA with one-dimensional channels. This structural evolution endows Co-CB-HPBTA with a high C2H2 adsorption capacity of 103.2 cm3/g (4.61 mmol/g) at 298 K and 1 bar, along with superior selectivity for C2H2/CO2 (10.6) and C2H2/C2H4 (13.3). Breakthrough experiments confirm its excellent separation performance for both mixtures under varied conditions, demonstrating efficient recovery of high-purity C2H2 and C2H4 with remarkable cyclic stability and humidity tolerance. The separation mechanism is elucidated by DFT calculations and in situ single-crystal-ray diffraction, which reveal enhanced binding interactions within the partitioned cages through multiple van der Waals contacts, rationalizing the high selectivity.