Tunable π ‐Basic Platforms in Porous Crystals for Enhanced C ₂ H ₂ /CO ₂ Separation at Elevated Temperature

ABSTRACT The adsorptive separation of acetylene (C ₂ H ₂ ) from carbon dioxide (CO ₂ ) at elevated temperatures presents a significant industrial challenge, yet offers substantial potential for energy savings. Here, we report a tunable π ‐basic platform within a family of porous coordination polymers (PCPs), derived from NTU‐65 , a soft framework that exhibits C ₂ H ₂ ‐specific gate‐opening behavior. Through systematic ligand functionalization with plana, π ‐conjugated units, we precisely engineered the framework's pore chemistry. The optimal material, NTU‐65‐th , confines C ₂ H ₂ via a dual chelation mode: its two carbon atoms engage with densely packed π systems, while its two hydrogen atoms interact with electronegative anions, generating a selective trapping effect, not observed for CO ₂ . This mechanism, verified by modeling and In situ spectroscopy, creates a significant difference in binding energies. As a result, NTU‐65‐th achieves both high C ₂ H ₂ uptake and promising C ₂ H ₂ /CO ₂ separation at 353 K, along with facile regeneration. This work demonstrates that precise pore chemistry modulation can overcome the trade‐off between affinity and selectivity at elevated temperature, offering a new route for advancing energy‐efficient separation materials.