Molecular Sieving and Direct Visualization of CO 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 CO at ambient conditions. Notably, CO molecules can be precisely observed in the single-crystal structure of NKMOF-3-Ln. Highly ordered CO molecules can strongly interact with the framework via electrostatic interaction of nitrates. We found that the CO adsorption capacity and binding energy were gradually enhanced as lanthanide contraction. The strong CO binding affinity endows NKMOF-3-Ln with excellent CO separation performance, which is verified by experimental breakthrough results. Moreover, because of the specific binding affinity of CO, NKMOF-3-Eu showed a fluorescence response to CO.