Direct air capture (DAC) is a promising negative-emission technology for mitigating climate change caused by excessive atmospheric CO2 emissions. Amine-functionalized solid adsorbents exhibit a strong affinity for CO2 in ambient air, making them attractive for DAC systems. However, their regeneration for reuse typically requires a high energy use during thermal swing processes. Herein, we upcycle wood waste into a DAC adsorbent that can release CO2 via solar light irradiation for an energy-saving DAC process. Importantly, the as-synthesized adsorbent in situ preserves lignin, enabling photothermal heating without addition of photothermal fillers into a complex composite. The as-synthesized adsorbent exhibits a CO2 uptake of 1.84 mmol/g at 25 °C, rapidly reaching 50% of its capacity within 7 min, and releasing 50% of CO2 in 22 min at 67 °C under solar illumination. Moreover, this study found the presence of water vapor enhances the CO2 adsorption capacity of the adsorbent, making it particularly advantageous for CO2 capture under humid air conditions. This work demonstrates a straightforward approach for developing solar-driven regenerative CO2 adsorbents based to a large fraction on waste lignocellulosic biomass, offering a promising pathway to sustainable and energy-efficient DAC.
Qi et al. (2026) studied this question.