Experimental strategies on enhancing toxic gases uptake of metal–organic frameworks

In conjunction with economic development and world population growth, human health is seriously jeopardized by human-made by-products released into the atmosphere or aquatic media. Among them, ammonia (NH3) and volatile organic compounds (VOCs) are produced daily as toxic chemicals. In addition, many sulfur-containing compounds are highly corrosive with severe impacts on human health, particularly hydrogen sulfide (H2S) and sulfur dioxide (SO2), as extremely hazardous ones. Therefore, more focus should be dedicated to advanced materials with high uptake capacity and high performance for the removal of such compounds. Metal-organic frameworks (MOFs), as coordinated polymers, are in the category of crystalline, porous, hybrid materials, which are composed of metal clusters-based nodes and organic ligands as linkers. Due to the variety of accessible organic ligands and inorganic metals, many versatile MOFs can be synthesized with adjustable pore size, large internal surface area, extensive porosity, and controllable functionality. In this review, achievements in the design and synthesis of functionalized/modified MOFs, as novel adsorbents for removing NH3, H2S, SO2, and VOCs, have been presented. Interestingly, based on the basicity of toxic gases, modified MOFs containing Lewis acid sites or missing linker defective sites showed more adsorption capacity than some pristine MOFs.