Efficient and selective capture of sulfur dioxide by graphitic phase carbon nitride equipped with BmimCl-type deep eutectic solvents.

Deep eutectic solvents(DESs) are adsorbents for SO2 capture. Their industrial application remains constrained by the high viscosity of the SO2-loaded liquid and associated transport difficulties. To address this limitation, DESs (BmimCl:Im) were immobilized onto graphitic carbon nitride(g-C3N4) with a well-developed pore structure. Composite materials with different loading ratios were prepared by physical impregnation,and their SO2 capture performance was systematically evaluated. g-C3N4 is composed of stacked nanosheets that form flexible nanoporous channels, providing high loading capacity, and preserving a stable solid morphology after DES loading, which markedly reduces DES viscosity. At 25 °C and 1 bar, the nDESs@g-C3N4 composite achieved a maximum SO2 adsorption capacity of 12.89 mmol/g, exceeding that of most reported solid adsorbents. This performance can be attributed the porous structure of g-C3N4 and multiple interactions between DESs and SO2. The Cl- anion in the DES exhibits strong electron-donating ability and weak basicity associated with tertiary nitrogen, resulting in high selectivity toward SO2 over CO2 and N2. The composite retained excellent adsorption capacity after ten adsorption-desorption cycles. These results indicate that nDESs@g-C3N4 is a promising candidate for SO2 capture from industrial exhaust gases.