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

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 (socalled 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.
Competing Interests: Conflicts of interest There are no conflicts to declare.