Boosting SO2 Capture within Nitrogen-Doped Microporous Biocarbon Nanosheets

The capture of corrosive SO2 is of great importance in power plants but remains an energetically challenging process. We herein report a strategy to boost SO2 capture under low partial pressure conditions using cost-effective bio-resourced porous carbons (PCs), which involves controlling the microporosity and nitrogen content of nanosheet-like biocarbons to enhance interactions with SO2. This approach uses inexpensive biomass-derived humic acid as a precursor and melamine as a nitrogen source, where the N-doping level, porosity, and morphology are effectively regulated by Pluronic P123-induced self-assembly. The obtained PCs revealed a new record-high adsorption capacity (7.9 mmol/g at 25 °C/0.25 bar) for SO2 with an acceptable recyclability (over three cycles), which exceeded state-of-the-art porous sorbents. The strong affinity toward SO2, which was exemplified by in situ spectroscopic investigations and quantum-chemical calculations, was mainly attributed to strong hydrogen bonding of SO2 with −CH2 or −CH groups adjacent to the nitrogen atoms in the backbone as opposed to SO2-nitrogen interactions. This method opens a novel route to the preparation of biocarbon materials exhibiting specific morphologies and high porosities, in addition to contributing to the development of a potential method for the capture of SO2 by tailorable PCs in industrial processes.