Synergistic engineering of 2D morphology and ultramicropores in lignin-derived carbon nanosheets for high-performance CO2 capture and solar-driven regeneration

Developing biomass-derived porous carbon adsorbents that simultaneously exhibit high CO 2 uptake, excellent CO 2 /N 2 separation performance, and low-energy regeneration capability is of great significance for efficient carbon capture. Herein, using sodium lignosulfonate as the carbon precursor and potassium oxalate monohydrate as an in situ template/activating agent, a one-step co-pyrolysis strategy was proposed for the targeted construction of ultrathin lignin-derived carbon nanosheets (ULCNs). This strategy enables the simultaneous regulation of two-dimensional sheet-like morphology, CO 2 size-matched ultramicropores, and O/S-containing polar sites. ULCN800 shows a loosely stacked nanosheet architecture with an apparent thickness of approximately 14.6 nm and an ultramicropore volume of 0.362 cm 3 g −1 , achieving high CO2 adsorption capacity at 273 K/1 bar (8.85 mmol g −1 ) and 298 K/1 bar (5.58 mmol g −1 ) and rapid photothermal-driven desorption under 1 kW m −2 irradiation. In contrast, ULCN600 exhibits the highest low-pressure CO 2 uptake (2.03 mmol g −1 at 298 K/0.15 bar) and enhanced CO 2 /N 2 selectivity, attributed to the retention of polar surface functional groups. Theoretical calculations and correlation analysis suggest that ultramicropores strongly associated with CO 2 capacity at high pressures, whereas O/S surface groups contribute to low-pressure affinity and selectivity. This study provides a strategy for tuning pore structure, surface chemistry, and photothermal properties in lignin-derived carbons for low-energy, regenerable CO2 capture.