Mg-Engineered Electronic Reconstruction and Dual Active Sites in SnO2 for Durable Photocatalytic Toluene Mineralization.

Photocatalyst deactivation remains a critical challenge for the practical application of photocatalytic air purification. Herein, a Mg2+-doped SnO2 catalyst with dual active sites-Mg2+ dopants and oxygen vacancies (OVs) was synthesized via in situ Mg2+ introduction to address the severe deactivation of SnO2 during toluene degradation, primarily caused by benzaldehyde accumulation. The Mg/SnO2-5 catalyst reaches 95.77% of its photocatalytic activity over five consecutive cycles (335 min) and exhibits excellent long-term stability during continuous operation (720 min), far surpassing pristine SnO2. Notably, this photocatalyst can also be synthesized from untreated bischofite, achieving a catalytic activity of up to 90%. Combined experimental and theoretical analyses reveal that: (i) Mg2+ doping induces electron localization, which is beneficial to inhibit charge recombination and promote deep mineralization of intermediates; (ii) increased active site density enhances toluene adsorption and conversion, reducing deactivation risks; and (iii) the modification lowers the Gibbs free energy barriers for both benzyl radical formation and the subsequent deep oxidation of benzaldehyde, thereby thermodynamically promoting ring-opening and mineralization, while preventing active-site blockage. These synergistic effects prevent active site blockage and ensure sustained photocatalytic activity. This work offers a viable strategy for designing stable and efficient photocatalysts against aromatic volatile organic compounds.