Synthesis and characterization of adsorbents for direct air CO2 capture

Abstract

The escalating concentration of CO2 in the atmosphere contributes to global warming, intensifying the adverse impacts of climate change. To mitigate these effects, there is a pressing need for efficient CO2 capture technologies to address the challenges of climate change. The adsorption process stands out as an effective and economically viable decarbonization method for capturing and reducing CO2 emissions from both anthropogenic sources and ambient air. However, achieving competitiveness and efficacy requires careful attention to the synthesis and modification of adsorbents. The critical factors for successful CO2 capture, especially in low-concentration environments like ambient air (400 ppm CO2) and indoor air (>400 ppm CO2), include the selection of a suitable adsorbent and its large-scale synthesis. Essential features for a new adsorbent design encompass high CO2 adsorption capacity, superior CO2/N2 selectivity, fast adsorption kinetics, low desorption energy, prolonged thermo-chemical stabilities, and cost-effective synthesis. In the present study, emphasis has been given on designing and enhancing diverse micro, mesoporous, and hierarchical silica-based adsorbents. This includes the incorporation of silica in metal-organic frameworks such as MIL-101(Cr), along with the utilization of hierarchical and nano silica, for the capture of CO2 from simulated (400 ppm CO2 in helium) and indoor air (>400 ppm CO2). Key discoveries from these investigations are outlined herewith.