CO2 capture from dilute sources using triamine functionalized MCF silica at ambient temperature

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A series of mesocellular siliceous foams (MCFs) with three-dimensional (3D) interconnected porous structure and tunable porosity were synthesized as supports to prepare triamine grafted sorbents using N’-[2-(3-trimethoxysilylpropylamino)ethyl]ethane-1,2-diamine for CO2 capture, particularly focusing upon the impact of pore structure of support on the adsorptive properties of final sorbents. The results indicate that both pore volume and diameter of MCF played a critical role in both CO2 adsorption capacity and kinetics at ambient temperature. Tested at 25 °C, the sorbent prepared by MCF with a large pore size of 33.7 nm and pore volume of 3.24 cm3/g exhibited remarkable CO2 adsorption capacity at low CO2 concentrations, which could achieve 2.14 mmol/g at 0.15 bar CO2 and 1.34 mmol/g under simulated air of 500 ppm CO2. Advanced characterization demonstrated that the increasing pore volume and diameter led to an increase of amine density on the MCF surface, which could enhance the steric hindrance and reduce the amine efficiency for CO2 adsorption at ambient temperature. It was also found that large pore size benefits the CO2 adsorption kinetics as the t80 and t90 of sorbents decreased with an increasing pore size of support. Moreover, the MCF-based sorbents exhibited superior thermo-stability with no adsorption loss during 50 cyclic adsorption-desorption tests. These results highlighted that the 3D MCF is a promising material for preparing amine grafted sorbents for flue gas CO2 capture and air purification applications.