Porous metal–organic frameworks as emerging sorbents for clean air

Sulfur dioxide and nitrogen oxides generated by anthropogenic activities are air pollutants that cause serious environmental problems and pose substantial health threats. Although established methods for emission desulfurization and denitrogenation already exist, more efficient and flexible technologies are still required. In this Review, we highlight state-of-the-art examples in which metal–organic frameworks (MOFs), an emerging class of porous sorbents, have been applied to the adsorptive removal of SO2 and NO2. MOFs can simultaneously exhibit superior adsorption capacities and exceptional selectivities for SO2 and NO2 in the presence of other flue and exhaust gases while maintaining their structural integrity. The highly crystalline nature and rich chemical functionality of MOFs have enabled the elucidation of host–guest interactions at a molecular level to afford insights and new knowledge that will inspire and inform the design of new generations of adsorbents. SO2 and NO2 are primary causes of air pollution and severe breathing problems worldwide. This Review gives an overview of the recent advances in the use of metal–organic framework materials to capture and remove these toxic gases from air.