Highly selective capture of SO2 with supported micro-mesoporous silica sphere from CO2-rich environment

Selective adsorption of sulfur dioxide (SO2) is an important clean technology for purification of exhaust gas from fossil fuel combustion. The widely applied zeolite-based adsorbents interact with SO2 through weakly physical adsorption, resulting in low adsorption capacity and selectivity for SO2. Herein, a facile strategy that combines improving the textural property of zeolite and optimizing adsorption sites is developed for efficient and stable SO2 adsorption. The micro-mesoporous silica sphere (MS) with high specific surface area and well-defined pore structure is obtained through a micelle expander assisted soft-template method, which can facilitate the dispersion and exposure of designed adsorption sites- methylated polyethyleneimine (mPEI). Since the Lewis basic sites of N in mPEI can strongly interact with the pi-receptor SO2, and the tertiary amine groups exhibit a weak attraction for CO2, the optimized MS supported mPEI adsorbent exhibits remarkable SO2 adsorption performance (7.5 mmol/g), exceptionally high SO2/N2 selectivity (16673) and SO2/CO2 selectivity (551). Moreover, it presents an outstanding stability in the adsorption-regeneration test. This work sheds light on the design of high-performance organic-solid composite adsorbent for selective capture of SO2.