Sustainable production of nitrogen-doped hierarchical porous carbons from fruit peel wastes for high-performance CO₂ capture

Global warming, driven by rising CO₂ levels, necessitates the development of sustainable carbon capture technologies. In addition to addressing climate change, there is an urgent need for environmentally responsible strategies to manage food waste. This study introduces a sustainable and versatile approach for converting fruit peel waste into nitrogen-doped carbon materials with hierarchical porous architectures, designed to enhance CO₂ capture performance. Using four types of fruit peels, orange, mandarin, pomelo, and banana, as model precursors, the synthesis combines hydrothermal carbonization (HTC) treatment and KOH activation, resulting in carbons with interconnected macropores and tunable micro−/mesoporosity. The hierarchical pore network ensures efficient gas diffusion, while the incorporated nitrogen functionalities, derived from intrinsic proteins and amino acids, enhance CO₂ affinity through strong adsorbent–adsorbate interactions. Among the synthesized materials, pomelo-derived activated carbon achieved the highest low-pressure CO₂ uptake of 1.66 mmol/g at 0.1 bar and 25 °C, setting a new benchmark among biomass-derived carbons. Meanwhile, banana-derived carbon activated at 800 °C reached a surface area of 1787 m²/g, underscoring the influence of pyrolysis conditions on textural development. These results highlight the synergistic benefits of nitrogen doping and hierarchical porosity, offering a scalable and sustainable route for biowaste valorization and advanced carbon capture.