Tunable π-Basic Platforms in Porous Crystals for Enhanced C₂H₂/CO₂ Separation at Elevated Temperature

The adsorptive separation of acetylene (C₂H₂) from carbon dioxide (CO₂) 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 C₂H₂-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 C₂H₂ 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 CO₂. 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 C₂H₂ uptake and promising C₂H₂/CO₂ 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.