An overview of the materials and methodologies for CO2 capture under humid conditions

CO2 capture is one of the cardinal technologies to combat the ever-escalating CO2 concentration in the atmosphere and to address the global climate change. Among the several strategies employed, adsorption on a porous solid seems to be a promising alternative to conventional CO2 capture technologies. However, to employ this technology under real-world CO2 capture conditions, the stability of the adsorbent materials under humid conditions is of paramount importance. To date, several CO2 sorbent materials have been reported to show remarkable CO2 uptake capacities both by physical and chemical adsorption. Nevertheless, the stability of many of these superior adsorbents under humid conditions is questionable. This is a key issue that hinders their commercial exploration under real flue gas conditions. The systematic tuning of material properties such as porosity, wettability, and hydrophobicity and functionalization strategies can play a decisive role in enhancing the material stability and CO2 sorption capacity. Herein, we present a comprehensive review of the trends and innovations in CO2 capture under humid conditions. Various materials and methodologies employed for CO2 capture from a humid stream are extensively reviewed. In particular, some of the key strategies such as tuning the hydrophobicity, amine modifications, introduction of polar functional groups, and water enhanced CO2 uptake are discussed in detail. We believe that the present review can lead this emerging field to develop state-of-the-art materials that can have a potential future in real-world CO2 capture technologies.