Modulating Acetylene Recognition in Boron Cluster Anion-Pillared Supramolecular Frameworks via Ligand Functionalization

Acetylene (C₂H₂) and ethylene (C₂H₄) are essential raw materials in the chemical industry, and producing them in high purity necessitates the efficient separation of C₂H₂/CO₂ and C₂H₂/C₂H₄ mixture─a challenging task due to their similar physical properties. Herein, we report the first example of a ligand-functionalized borane-cluster-based hybrid supramolecular metal-organic framework, denoted BSF-12, which integrates a hydroxyl-functionalized organic ligand (dpg) with inorganic boron cluster anions. This dual-functionalization strategy endows BSF-12 with exceptional adsorption and separation performance. The material exhibits high IAST selectivities of 12.0 for C₂H₂/CO₂ (50/50, v/v) and 11.7 for C₂H₂/C₂H₄ (1/99, v/v), outperforming many previously reported high-performance adsorbents. BSF-12 demonstrates outstanding stability, maintaining its structural integrity after exposure to air and water for 10 days. Dynamic breakthrough experiments confirmed its practical separation capability and excellent cyclic stability. DFT calculations reveal that the synergistic cooperation between the functional hydroxyl groups from the dpg ligand and the hydride sites from the [B₁₂H₁₂]²⁻ anion creates a robust recognition environment for C₂H₂, driving its selective adsorption. This work establishes a new paradigm for the design of advanced boron cluster-based frameworks for key gas separations.