Adsorption Interface-Induced H...F Charge Transfer in Ultramicroporous Metal-Organic Frameworks for Perfluorinated Gas Separation

Fluorinated electron gases (F-gases) are widely used in semiconductor manufacturing because of their unique plasma reactivity with silicon-based semiconductor materials. However, the low conversion efficiency of these F-gases in the plasma process makes the vent gases contain a certain concentration of F-gases, which causes environmental pollution and global warming. In this study, three ultramicroporous metal-organic frameworks M₃(HCOO)₆ (M = Co, Ni, Mn) were prepared for the separation and purification of F-gases through H...F interaction-induced charge transfer on the pore surface. Impressive F-gas adsorption capacities and record breakthrough selectivities for NF₃/N₂, CF₄/N₂, and SF₆/N₂ mixtures were achieved in M₃(HCOO)₆ MOFs. Density-functional theory (DFT) calculations and grand canonical Monte Carlo (GCMC) simulation studies demonstrated that the adsorption-induced charge exchange between the F atom in F-gases and the H atom in HCOO- accounts for the high performance of F-gases/N₂ separation. Systematic experimental investigations including equilibrium gas adsorption, instant adsorption rates, and dynamic breakthrough experiments also confirmed the efficient performance of M₃(HCOO)₆ MOFs for F-gas capture.