Topological Design of Unprecedented Metal-Organic Frameworks Featuring Multiple Anion Functionalities and...

Separation of acetylene (C₂ H₂ ) from carbon dioxide (CO₂ ) or ethylene (C₂ H₄ ) is industrially important but still challenging so far. Herein, we developed two novel robust metal organic frameworks AlFSIX-Cu-TPBDA (ZNU-8) with znv topology and SIFSIX-Cu-TPBDA (ZNU-9) with wly topology for efficient capture of C₂ H₂ from CO₂ and C₂ H₄ . Both ZNU-8 and ZNU-9 feature multiple anion functionalities and hierarchical porosity. Notably, ZNU-9 with more anionic binding sites and three distinct cages displays both an extremely large C₂ H₂ capacity (7.94 mmol/g) and a high C₂ H₂ /CO₂ (10.3) or C₂ H₂ /C₂ H₄ (11.6) selectivity. The calculated capacity of C₂ H₂ per anion (4.94 mol/mol at 1 bar) is the highest among all the anion pillared metal organic frameworks. Theoretical calculation indicated that the strong cooperative hydrogen bonds exist between acetylene and the pillared SiF₆ ^2- anions in the confined cavity, which is further confirmed by in situ IR spectra. The practical separation performance was explicitly demonstrated by dynamic breakthrough experiments with equimolar C₂ H₂ /CO₂ mixtures and 1/99 C₂ H₂ /C₂ H₄ mixtures under various conditions with excellent recyclability and benchmark productivity of pure C₂ H₂ (5.13 mmol/g) or C₂ H₄ (48.57 mmol/g).