Porous Metal–Organic Frameworks for Carbon Dioxide Adsorption and Separation at Low Pressure

The rapidly increasing concentration of CO2 in the atmosphere has resulted in a serious greenhouse effect. CO2 capture and storage (CSS) technology is widely accepted as an effective method for reduction of CO2 emissions. Metal–organic frameworks show an excellent potential for CO2 capture in CCS due to various advantages of high porosity, high surface area, adjustable pore structure, and multifunctionality. A series of works have been devoted to design of MOFs for CO2 capture and separation. Considering the low CO2 partial pressure in the practical industry, improving CO2 adsorption and separation performance at low pressure (including atmospheric pressure) is more meaningful. Establishing the structure–property relationships between MOFs and guest CO2 molecules is helpful for the design of MOFs as CO2 adsorbents. Therefore, we comprehensively review the factors which affect the CO2 capture performance on MOFs at low pressure, including pore structure, open metal sites, Lewis basic groups, and other polar groups. We further indicate the regulation of increasing CO2 uptake on modified MOFs through adsorption mechanisms based on clarified structures of MOFs. In addition, we discuss the strategies to improve separation performance of CO2 from flue gases, biogases, and crude C2H2 based on enhancement of CO2 uptake or sieving via porosity.