Abstract <p>Volatile organic compounds (VOCs) emissions are often accompanied by water vapor, which can significantly decrease the adsorption efficiency of activated carbon (AC) and other conventional adsorbents. As a result, the hydrophobic modification of AC and other primary adsorption materials has emerged as a key area of research. In this study, we successfully synthesized hydrophobic AC modified with stearyl chloride (SC). This modification leverages the ability of SC to acylate the hydrophilic hydroxyl functional groups on the AC surface. We systematically evaluated the adsorption performance and mechanisms of SC-modified AC for toluene under high-humidity conditions. Experimental results demonstrated that the toluene adsorption capacity of SC-AC-H was 1.68 times greater than that of unmodified AC, while its water vapor adsorption capacity was reduced to 25.78% of that of the unmodified AC at 27&#xa0;°C and 77% relative humidity. The dynamic adsorption behavior was well described by the Yoon–Nelson model. To further understand the competitive adsorption mechanism between toluene and water molecules, we employed the independent gradient model method to analyze the intermolecular interactions between SC and toluene. Overall, SC modification significantly enhanced the hydrophobicity of AC, thereby improving its adsorption efficiency for VOCs under high-humidity conditions. These findings highlight the potential of SC-modified AC as a promising solution for VOCs removal in challenging environmental settings.</p> Graphical abstract <p></p>