Mg‐Engineered Electronic Reconstruction and Dual Active Sites in SnO ₂ for Durable Photocatalytic Toluene Mineralization

ABSTRACT

Photocatalyst deactivation remains a critical challenge for the practical application of photocatalytic air purification. Herein, a Mg ²⁺ ‐doped SnO ₂ catalyst with dual active sites‐Mg ²⁺ dopants and oxygen vacancies (O _Vs ) was synthesized via in situ Mg ²⁺ introduction to address the severe deactivation of SnO ₂ during toluene degradation, primarily caused by benzaldehyde accumulation. The Mg/SnO ₂ ‐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 SnO ₂ . 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) Mg ²⁺ 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.