<p>In the controlled synthesis of biomass-derived porous carbon materials, effective pretreatment strategies play a critical role in modulating the chemical activation process and optimizing material performance. However, existing studies predominantly focus on the macroscopic structural changes induced by pretreatment, often overlooking the important role of chemical composition evolution during activation. Herein, a coconut shell-based acidic hydrothermal pretreatment was designed to precisely control the evolution of the primary pore structure alongside the enhanced retention of oxygen species in the hydrochar. Subsequent chemical activation successfully yields a high-performance carbon material with a well-defined hierarchical porous structure. This material exhibits a high specific surface area of 1963 m² g⁻¹ and delivers an outstanding specific capacitance of 420&#xa0;F g⁻¹ at a current density of 0.5&#xa0;A g⁻¹. When assembled into a solid-state supercapacitor, the device achieves a high energy density of 12.97 Wh kg⁻¹. It also demonstrates excellent cycling stability, retaining 97.02% of its initial capacitance after 10,000 cycles at 10&#xa0;A g⁻¹, along with a high Coulombic efficiency of 99.84%. Our findings reveal that appropriate acidic hydrothermal pretreatment not only establishes a continuous primary pore network within the precursor—facilitating the deep diffusion and uniform reaction of the activating agent—but also enhances activation efficiency synergistically through the anchoring effect of oxygen species. This work provides new insights and experimental support for the rational design of high-performance biomass-derived carbon materials.</p> Graphical abstract <p></p>