Mn-doped geopolymers photocatalysts with sustained-release OH− for highly efficient degradation of malachite green and tetracycline

Hydroxyl radicals (•OH) are the primary reactive groups in photocatalytic reactions. However, the stability and long-term effectiveness of photocatalysis in degrading dye wastewater and antibiotic contaminants remains a major challenge. In this study, the sustained-release microspheres containing OH− were prepared by Mn-doped metakaolin-based geopolymers (Mn-MGPs), and a strategy combining defect engineering and OH− sustained-release was presented. A large number of oxygen vacancies (O), which can enhance the light absorption properties, can generate superoxide radicals (O2•-) on the catalyst surface and promote the formation of (•OH) to fabricate efficient heterojunction photocatalysts. The photocatalysts were systematically characterized for photocatalytic activity and long-term effectiveness in the degradation of malachite green (MG) and tetracycline (TC). The mechanism of the enhanced photocatalytic performance of the catalysts was investigated by characterization and DFT theoretical calculations, and the pollutant degradation pathway was proposed. This study provides an innovative approach to the controlled design of valence heterostructures.