Exquisitely Constructing a Robust MOF with Dual Pore Sizes for Efficient CO₂ Capture

Developing metal-organic framework (MOF) adsorbents with excellent performance and robust stability is of critical importance to reduce CO₂ emissions yet challenging. Herein, a robust ultra-microporous MOF, Cu(bpfb)(bdc), with mixed ligands of N, N'-(1,4-phenylene)diisonicotinamide (bpfb), and 1,4-dicarboxybenzene (bdc) was delicately constructed. Structurally, this material possesses double-interpenetrated frameworks formed by two staggered, independent frameworks, resulting in two types of narrow ultra-micropores of 3.4 × 5.0 and 4.2 × 12.8 Ų, respectively. The above structural properties make its highly selective separation at 273~298 K with a CO₂ capacity of 71.0~86.2 mg/g. Its adsorption heat over CO₂ and IAST selectivity were calculated to be 27 kJ/mol and 52.2, respectively. Remarkably, cyclic breakthrough experiments corroborate its impressive performance in CO₂/N₂ separation in not only dry but also 75% RH humid conditions. Molecular simulation reveals that C-H···O_CO2 in the pores plays a pivotal role in the high selectivity of CO₂ adsorption. These results point out the huge potential application of this material for CO₂/N₂ separation.