Novel Synthesis of Phosphorus-Doped Porous Carbons from Lotus Petiole Using Sodium Phytate for Selective CO2 Capture

Developing sustainable and high-performance sorbents for efficient CO2 capture is essential for mitigating climate change and reducing industrial emissions. In this study, phosphorus-doped porous carbons (LPSP-T) were synthesized via a one-step activation–doping strategy using lotus petiole biomass as a precursor and sodium phytate as a dual-function activating and phosphorus-doping agent. The simultaneous activation and phosphorus incorporation at various temperatures (650–850 °C) under a nitrogen atmosphere produced carbons with tailored textural properties and surface functionalities. Among them, LPSP-700 exhibited the highest specific surface area (525 m2/g) and a hierarchical porous structure, with abundant narrow micropores (<1 nm) and phosphorus-containing surface groups that synergistically enhanced CO2 capture performance. The introduction of P functionalities not only improved the surface polarity and binding affinity toward CO2 but also promoted the formation of a well-connected pore network. As a result, LPSP-700 delivered a CO2 uptake of 2.51 mmol/g at 25 °C and 1 bar (3.34 mmol/g at 0 °C), along with a high CO2/N2 selectivity, fast CO2 adsorption kinetics and moderate isosteric heat of adsorption (Qst). Furthermore, the dynamic CO2 adsorption capacity (0.81 mmol/g) was validated by breakthrough experiments, and cyclic adsorption–desorption tests revealed excellent stability with negligible loss in performance over five cycles. Correlation analysis revealed pores < 2.02 nm as the dominant contributors to CO2 uptake. Overall, this work highlights sodium phytate as an effective dual-role agent for simultaneous activation and phosphorus doping and validates LPSP-700 as a sustainable and high-performance sorbent for CO2 capture under post-combustion conditions.