This study explores the development of urea-functionalized hydrochar from Leucaena leucocephala wood (LW) for CO₂ capture. Hydrochar was produced via hydrothermal carbonization at 170 °C for 90 min and subsequently functionalized with urea. The effects of urea: hydrochar ratio (1:1 to 3:1), activation temperature (400–800 °C), and heating rate (5–15 °C/min) on CO₂ adsorption capacity were investigated. Optimal conditions (2:1 urea: hydrochar ratio, 600 °C activation temperature, 5° C/min heating rate) increased CO₂ adsorption capacity from 13.09 mg/g to 76.20 mg/g. The modified adsorbent demonstrated high affinity towards CO₂ over N2, CH4, and O₂, and maintained performance over 11 adsorption–desorption cycles. Kinetic studies revealed physisorption as the primary adsorption mechanism. In fixed-bed column tests, best performing conditions within the tested ranges (30 ml/min flow rate, 15% CO₂ concentration, 30 °C) yielded a CO₂ uptake of 195.54 mg/g. This study demonstrates the potential of urea-functionalized hydrochar from Leucaena leucocephala as an efficient, sustainable adsorbent for CO₂ capture.
