Isoreticular Double Interpenetrating Copper–Pyrazolate–Carboxylate Frameworks for Efficient CO2 Capture

It is highly desired to develop a porous adsorbent for selective CO2 capture from flue gas, which meets the goal of environmental protection and energy safety. Herein, three isoreticular Cu(II)–pyrazolate–carboxylate frameworks (FJU-26, FJU-27, and FJU-28) were constructed through regulation of the ligand size. Among them, FJU-27 was constructed using the ligands (H2NDI: 2,7-bis(3,5-dimethyl) dipyrazol-1,4,5,8-naphthalene tetracarboxydiimide and H2BDC: 1,4-dicarboxybenzene) with appropriate lengths, which gave multipoint intermolecular hydrogen-bonding interactions and resulted in a robust structure with suitable pore size and affinity toward CO2. As expected, FJU-27a exhibited a higher CO2 uptake capacity (2.54 mmol g–1) under ambient conditions with an uptake ratio of 5.3 for CO2/N2 gas systems, in contrast to 0.92 mmol g–1 and 1.9 for the flexible FJU-28a, while a collapse occurred in FJU-26a (the activated samples were named FJU-26a, FJU-27a, and FJU-28a, respectively). Moreover, the higher selectivity of CO2 for FJU-27a was ascertained by configurational bias Monte Carlo molecular simulations. Meanwhile, dynamic breakthrough experiments of FJU-27a toward a CO2/N2 mixture proved to be a potential candidate for the synthesis of a practical metal–organic framework for CO2 capture.