Development and progress of functionalized silica-based adsorbents for CO2 capture

The severe environmental and economic impacts of greenhouse gas (GHG) emissions have directed the research towards carbon dioxide CO2 capture and sequestration. Over the years, many new processes/materials have been developed to control CO2 emissions. To date, amine scrubbing process is the popular method which is widely used on an industrial scale especially post-combustion plant. But the exorbitant cost of regeneration and serious environmental impacts because of traditional amine solvents make this process unattractive for large scale applications. This issue requires attention towards the development of advanced processes/materials with improved efficiency. Ionic liquids (ILs) with their adjustable physicochemical properties such as cation/anion pairing, viscosity and vapor pressure can easily replace traditional amine solvents in absorption. However, the high cost and increased viscosity of ILs hinder large-scale applications. Additionally, new advanced materials show excellent CO2 adsorption properties by a combined effect of amine moiety in IL and porous support. The focus of this review is to highlight the use of functionalized/non-functionalized ILs for CO2 capture. The role of cation/anion pair, fluorinated ILs, and alkyl chain length on CO2 solubility is observed and demonstrated with experimental findings. The adsorption of CO2 on the surface of functionalized silica by acid-base interaction mechanism as well as the position of amine moiety on IL results in different reaction stoichiometry being discussed in detail. This review highlights, the effect of various operating parameters on CO2 adsorption and the favourable conditions for sustainable CO2 capture. (C) 2021 Elsevier B.V. All rights reserved.