A metal-organic framework with suitable pore size and dual functionalities for highly efficient post-combustion CO 2 capture

Abstract

Capturing carbon dioxide (CO 2 ) 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 2 -capturing materials. However, it is challenging to target materials with both extremely high CO 2 capture capacity and gas selectivity (so-called trade-off) along with moderate regeneration energy. Herein, we developed a novel porous material, [Cu(dpt) 2 (SiF 6 )] n (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 2 capture capacity (3.56 mmol g −1 at 0.15 bar and 296 K) and CO 2 /N 2 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 2 capture capacity at the low-pressure region and the moderate heat of CO 2 adsorption can be attributed to the suitable pore size and dual functionalities (SiF6 2− and tetrazine), which not only interact with CO 2 molecules but also enable the dense packing of CO 2 molecules within the framework. Simulated and actual breakthrough experiments demonstrate that UTSA-120a can efficiently capture CO 2 gas from the CO 2 /N 2 (15/85, v/v) and CO 2 /CH 4 (50/50) gas mixtures under ambient conditions.