Molecular sieving and direct visualization of CO2 in binding pockets of an ultramicroporous lanthanide MOF platform

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