Molecular Sieving and Direct Visualization of CO₂ in Binding Pockets of an Ultramicroporous Lanthanide Metal-Organic Framework Platform

Inspired by the structure of carbonic anhydrase, we developed a robust ultramicroporous lanthanide metal-organic framework (MOF) platform (NKMOF-3-Ln), which possesses a porous pocket to selectively bind with CO₂ at ambient conditions. Notably, CO₂ molecules can be precisely observed in the single-crystal structure of NKMOF-3-Ln. Highly ordered CO₂ molecules can strongly interact with the framework via electrostatic interaction of nitrates. We found that the CO₂ adsorption capacity and binding energy were gradually enhanced as lanthanide contraction. The strong CO₂ binding affinity endows NKMOF-3-Ln with excellent CO₂ separation performance, which is verified by experimental breakthrough results.