Fully inverse adsorption enables one-step high-purity C2H2 separation from ternary C2 mixtures in a robust porous crystal

Abstract Direct harvesting of electronic-grade acetylene (C 2 H 2 ) from ternary C2 mixtures is a great challenge due to the ubiquitous adsorption preference of conventional porous materials (C 2 H 2 > ethylene (C 2 H 4 ) > ethane (C 2 H 6 )). Here, we report a strategy to reverse this selectivity by leveraging ligand functionalization in porous crystals. Through the incorporation of trifluoromethyl/methyl groups into a pyrazole-carboxylate linker, we engineer a series of MOF-5 analogs. The optimal material, NTU-98 , fully reverses the adsorption trend of C2 hydrocarbons (C 2 H 6 > C 2 H 4 > C 2 H 2 ), enabling direct production of C 2 H 2 with >99.99% purity from ternary feeds at room temperature in one-step. Combined density functional theory calculations and gas-loaded crystallographic analyses unveil the molecular mechanism: methyl groups precisely positioned within the cages enhance host-guest interactions with C 2 H 4 and C 2 H 6 , while suppressing the binding affinity for C 2 H 2 . This work presents a porous crystal for direct C 2 H 2 purification from ternary feeds and a blueprint for designing microporous environments targeting challenging separations.