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.