High and selective capture of low-concentration CO2 with an anion-functionalized ultramicroporous metal-organic framework

CO2 capture, especially under low-pressure range, is of significance to maintain long-duration human operation in confined spaces and decrease the CO2 corrosion and freezing effect for the liquefaction of natural gas. Herein, we for the first time report a novel anion-functionalized ZU-16-Co (TIFSIX-3-Co, TIFSIX=hexafluorotitanate (TiF62−), 3=pyrazine), which exhibits one-dimensional pore channels decorated by abundant F atoms, for efficient CO2 capture at a concentration around 400–10,000 ppm. Among its isostructural MFSIX-3 (M=Si, Ti, Ge) family materials, ZU-16-Co with fine-tuned pore size of 3.62 Å exhibits the highest CO2 uptake at 0.01 bar (10,000 ppm) and 1 bar (2.63 and 2.87 mmol g−, respectively). The high CO2 capture ability of ZU-16-Co originates from the fine-tuned pore dimensions with strong F⋯C=O host-guest interactions and relatively large pore volumes coming from its longer coordinated Ti-F-Co distance (3.9 Å) in c direction. The excellent carbon trapping performance was further verified by dynamic breakthrough tests for CO2/N2 (1/99 and 15/85) and CO2/CH4 (50/50) mixtures. The adsorption and separation performances, resulting from the fine-tuned pore system with periodic arrays of exposed functionalities, demonstrate that ultramicroporous ZU-16-Co can be a promising adsorbent for low-concentration carbon capture.