Interfacial engineering of MnO₂/Al₂O₃ catalyst for unique sulfur-promoted benzene oxidation at mild temperatures

Catalyst deactivation by sulfur poisoning remains a critical barrier to widespread industrial application. In this study, MnO₂/Al₂O₃ catalyst was prepared via a simple wet impregnation and in situ redox method. The abundant surface hydroxyl groups of Al₂O₃ facilitate the formation of Mn-O-Al bonds, creating an intimately contacted Mn-Al interface. Experimental and theoretical calculations reveal that the MnO₂/Al₂O₃ catalyst with an engineered interface exhibits enhanced sulfur resistance and sulfur-promoted activity for benzene oxidation compared to pure MnO₂. Interface structure alters the site of sulfur action, and the enhanced sulfur resistance is attributed to the preferential capture of SO₂ by interfacial oxygen, forming interfacial sulfates that protect the Mn active sites. The sulfur promotion originates from the formation of Mn-O-(SO₃)-Al interfacial structure with abundant defects. Interfacial electron transfer facilitates the formation of high-valent Mn⁴⁺ and electrophilic O^- species. Meanwhile, the interfacial sulfates act as strong acid sites that adsorb and attack benzene to promote ring-opening. Interface defects induce the formation of oxygen vacancies, which synergistically activate gas-phase oxygen and drive the deep oxidation of benzene. This work provides new insights into the design of sulfur-resistant catalysts.