Bridging the Stability–Performance Gap in Gas Separation: A Positive-Charge Framework with Open Metal Sites and N-Decorated Pores

The removal of carbon dioxide (CO₂) from natural gas is critical for pipeline integrity and downstream processing, yet it remains a challenging separation. While porous coordination polymers offer tunable platforms for this task, many frameworks sacrifice either high CO₂ affinity or hydrolytic robustness. Here, we report the rational design and synthesis of NTU-77, a stable copper-based framework assembled from an asymmetric ligand integrating pyridine, imidazole, and carboxylate functionalities. This strategic design yields a material that synergistically combines a positive-charge framework, accessible open metal sites, a nitrogen-decorated polar pore surface, and robust coordination bonds. NTU-77 exhibits good moisture stability (3 months) and demonstrates promising CO₂/CH₄ separation performance at 298 K. Breakthrough simulations confirm its potential under mixed-gas conditions. This work highlights the effectiveness of asymmetric multifunctional ligands in constructing adsorbents that bridge the gap between high selectivity and practical stability for energy-efficient gas purification.