A novel Cu₂LaO₄/ZSM-5 sorbent was synthesized using the sol–gel method, and the role of H₂S in enhancing Hg⁰ removal was investigated through experimental and theoretical approaches. Mercury removal performance was evaluated in a fixed-bed reactor under simulated syngas conditions, revealing that H₂S significantly promoted removal efficiency, achieving 95.6 % at 200 °C. In contrast, H₂ and CO inhibited Hg0 removal by depleting surface oxygen species. The addition of H₂S mitigated these effects, facilitating Hg0 adsorption and oxidation via a Langmuir–Hinshelwood mechanism. Density functional theory (DFT) calculations confirmed strong chemisorption of Hg0 and H₂S on the Cu₂LaO₄ surface, with adsorption energies of −123.71 kJ/mol and −168.98 kJ/mol, respectively. The reaction to form HgS had a manageable energy barrier of 25.80 kJ/mol and an exothermic enthalpy of −196.82 kJ/mol, with HgS formation as the rate-limiting step. This study highlights the effectiveness of Cu₂LaO₄/ZSM-5 for mercury capture and its potential application in industrial syngas purification.