Rational introduction of nitridizing agent to hydrothermal carbonization for enhancing CO2 capture performance of tobacco stalk-based porous carbons

•The nitridizing agents didn't necessarily increase the CO2 uptake of yielded carbon.•The PC/Urea exhibited CO2 uptakes of 4.83 mmol/g at 25 °C and 7.35 mmol/g at 0 °C.•The physicochemical properties of yielded carbon were changed by nitridizing agents.•The narrow micropores volume decided CO2 uptake for these carbons at low pressure.•The necessity to carefully select nitridizing agents for high CO2 capture performance.