Engineering solar-light-responsive TiO₂ nanosheets from deactivated Ti-based MOFs for enhanced photocatalytic performance

Here, a sustainable route for upcycling deactive Ti-based MOF into value-added TiO₂ photocatalysts is developed. The optimized upcycling protocol, executed at a calcination temperature of 500 ^∘C, yields TiO₂ nanosheets with a phase composition of 86.20 % anatase and 13.80 % rutile. These mixed phases indicate high crystallinity in the structure. The nanosheet architecture here, exhibits a surface area of 35 m² g⁻¹. Transformation of Ti-MOF into a crystalline TiO₂ structure with a clean oxide structure, beside microscopic observations, is also further confirmed by stabilization of Ti 2 p binding energies and sharpening of the O 1 s lattice oxygen peak. This nanostructure has a promising charge carrier dynamics, with an extended photo-generated carrier lifetime of 0.92 ns under 377 nm light excitation. Consequently, the resultant catalyst achieves a remarkable dTON of 274 μmol h⁻¹ g_cat⁻¹ and TOF of 2.62 × 10⁻⁴ s⁻¹ for oxytetracycline (OTC) degradation, 2-fold better than commercial P25. Robust efficacy in degrading recalcitrant contaminants, including methylene blue (MB), Congo red (CR), and diclofenac (DIF), is demonstrated under solar-light illumination. The intermediates of the oxidative degradation and mineralization processes were identified. Mechanistic studies verify the formation of O₂^·− radicals, leading the degradation.