<p>To address the problems of insufficient pore structure regulation and low yield in the preparation of biomass activated carbon (AC), a new method for the preparation of AC precursors based on supercritical carbon dioxide (sc-CO₂) pretreatment was developed in this study. High-performance AC adsorbent materials were systematically prepared from waste mushroom sticks (MSs) by supercritical CO₂ pretreatment combined with KOH activation process. The regulation of the pore structure of the AC materials by the pretreatment and activation process parameters was investigated, and the results showed that the pretreatment technology could significantly improve the adsorption performance and the preparation yield of the AC. Compared with direct activation of the MSs, the maximum yield increased by 4.31 times, the maximal pore volume increased by 25.24%, and the maximal specific surface area increased by 16.12%. The optimal conditions for the preparation of AC were as follows: activation temperature of 700&#xa0;°C, carbon to KOH ratio of 1:3, and activation time of 100 min.</p> Graphical abstract <p></p>