Ethylenediamine-assisted deconstruction and nitrogen functionalization of wheat straw into ultramicroporous carbons for CO2 capture

Developing biomass-derived porous carbons with tailored ultramicroporosity and surface chemistry is important for efficient CO 2 capture. In this study, ethylenediamine (EDA)-assisted hydrothermal pretreatment was combined with KOH activation to prepare nitrogen-functionalized porous carbons from wheat straw. Rather than introducing a fundamentally new activation chemistry, this work investigates whether the integration of lignocellulosic deconstruction and precursor-stage nitrogen incorporation can influence subsequent pore development and promote the formation of CO 2 -accessible ultramicropores. Spectroscopic and thermal analyses indicate that EDA treatment modifies the hydrochar framework, redistributes surface functional groups, and increases the nitrogen content from 1.23 to 8.67 at%. After KOH activation, the optimized NWSC600 exhibits a specific surface area of 1244 m 2 g −1 , a micropore volume of 0.507 mL g −1 , an ultramicropore volume of 0.292 mL g −1 , and a nitrogen content of 5.25 at%. NWSC600 achieves CO 2 uptakes of 7.3 mmol g −1 at 0 °C and 4.8 mmol g −1 at 25 °C at 1 bar, corresponding to increases of approximately 24% and 20%, respectively, compared with the EDA-free control. Correlation analysis and molecular simulations reveal that CO 2 capture is dominated by the synergistic contribution of narrow ultramicropores and polar N/O-containing active sites rather than surface area alone. This work offers a precursor-level chemical engineering route for upgrading agricultural waste into high-performance carbon adsorbents for CO 2 capture.