A metal-organic framework with suitable pore size and dual functionalities for highly efficient post-combustion CO capture.

Capturing carbon dioxide (CO) from flue gases with porous materials has been considered as a viable alternative technology to replace traditional liquid amine adsorbents. A large number of microporous metal-organic frameworks (MOFs) have been developed as CO-capturing materials. However, it is challenging to target materials with both extremely high CO capture capacity and gas selectivity (socalled trade-off) along with moderate regeneration energy. Herein, we developed a novel porous material, [Cu(dpt)(SiF)] (termed as UTSA-120; dpt = 3,6-di(4-pyridyl)-1,2,4,5-tetrazine), which is isoreticular to the net of SIFSIX-2-Cu-i. This material exhibits simultaneously high CO capture capacity (3.56 mmol g at 0.15 bar and 296 K) and CO/N selectivity (~600), both of which are superior to those of SIFSIX-2-Cu-i and most other MOFs reported. Neutron powder diffraction experiments reveal that the exceptional CO capture capacity at the low-pressure region and the moderate heat of CO adsorption can be attributed to the suitable pore size and dual functionalities (SiF6 and tetrazine) which not only interact with CO molecules but also enable the dense packing of CO molecules within the framework. Simulated and actual breakthrough experiments demonstrate that UTSA-120a can efficiently capture CO gas from the CO/N (15/85, v/v) and CO/CH (50/50) gas mixtures under ambient conditions.