Topology Reconfiguration of Anion‐Pillared Metal–Organic Framework from Flexibility to Rigidity for Enhanced Acetylene Separation

Abstract

Flexible metal-organic framework (MOF) adsorbents commonly encounter limitations in removing trace impurities below gate-opening threshold pressures. Topology reconfiguration can fundamentally eliminate intrinsic structural flexibility, yet remains a formidable challenge and is rarely achieved in practical applications. Herein, a solvent-mediated approach is presented to regulate the flexible CuSnF₆-dpds-sql (dpds = 4,4''-dipyridyldisulfide) with sql topology into rigid CuSnF₆-dpds-cds with cds topology. Notably, the cds topology is unprecedented and first obtained in anion-pillared MOF materials. As a result, rigid CuSnF₆-dpds-cds exhibits enhanced C₂H₂ adsorption capacity of 48.61 cm³ g^-1 at 0.01 bar compared to flexible CuSnF₆-dpds-sql (21.06 cm³ g^-1). The topology transformation also facilitates the adsorption kinetics for C₂H₂, exhibiting a 6.5-fold enhanced diffusion time constant (D/r²) of 1.71 × 10^-3 s^-1 on CuSnF₆-dpds-cds than that of CuSnF₆-dpds-sql (2.64 × 10^-4 s^-1). Multiple computational simulations reveal the structural transformations and guest-host interactions in both adsorbents. Furthermore, dynamic breakthrough experiments demonstrate that high-purity C₂H₄ (>99.996%) effluent with a productivity of 93.9 mmol g^-1 can be directly collected from C₂H₂/C₂H₄ (1/99, v/v) gas-mixture in a single CuSnF₆-dpds-cds column.