INORGANIC-ORGANIC HYBRID NANOPOROUS MATERIALS FOR CARBON DIOXIDE CAPTURE

Abstract

The looming threat of global warming owing to the unprecedented rise in the environmental CO2 level that reached as high as 408 ppm in recent times has forced the scientific community to find ways to restrict the use of fossil fuels for energy generation that emit a substantial amount of CO2 to the environment or find sustainable alternative energy sources. With so much of R&D activities in last decades, the contribution of the later to the total energy generation is not encouraging and hence, the former looks more realistic. Almost 41 billion ton of CO2 emitted annually into the atmosphere due to the fossil fuel burning, is required to be captured in order to have sustainable energy economy protecting the environment. Traditionally, organic liquid amine solutions have been utilized for tripping off CO2 from fossil fuel fired flue gas stream with an unacceptable financial burden. Use of the solid adsorbents has emerged as potential alternatives, as it could circumvent some of the disadvantages of the above method such as the ease of regeneration, thermal and hydrothermal stability. Solid adsorbents such as metal oxide, zeolites, activated carbon, amine grafted mesoporous silica, metal organic framework, covalent organic framework, porous aromatic framework have been utilized for the CO2 capture application with some hope for their potential use to trap the CO2 in the coal-fired power plants. After having a basic understanding about the principle governing the effective adsorption process, especially for CO2 capture, in the present research, the adsorbent materials have been synthesized utilizing precursors that could lead to the formation of materials with large and uniform distribution of heteroatoms. Two types of inorganic-organic hybrid nanoporous materials viz. (i) non-siliceous and (ii) siliceous hybrid materials have been made. The non-siliceous hybrid materials were synthesized using cyclophosphazene moiety via Schiff base and nucleophilic condensation that yielded materials with the maximum specific surface area of 976 and 1328 m2 g-1, respectively. The maximum CO2 capture capacity recorded was 22.8 wt% at 273 K and 1 bar. The siliceous hybrid materials were synthesized by condensation of cyanuric chloride with (3-aminopropyl)triethoxyxilane, N-[3- (trimethoxysilyl)propyl]ethylenediamine or N1-(3-trimethoxysilylpropyl)ethylenetriamine, followed by hydrolysis and polycondensation. The nitrogen content was tuned in these organosilica frameworks by taking pre-determined precursors. Moreover, the textural properties were improved by co-condensing with TEOS. The maximum estimated specific surface area recorded was 1304 m2 g-1 with a maximum CO2 uptake of 11.6 wt% at 273 K and 1 bar. All these synthesized materials have been characterized by state-of-the-art analytical techniques.