Highly Efficient Visible-Light Photocatalysts: Bi2O3@TiO2 Derived from Ti-MOFs for Eriochrome Black T Degradation: A Joint Experimental and Computational Study

Abstract

Herein, we synthesized Ti-MOF through a solvothermal method and subsequently calcined it to form anatase TiO2. We further developed a Bi2O3@TiO2 mixed oxide using impregnation and calcination processes. These oxides showed significant photocatalytic activity for degrading Eriochrome Black T (EBT) dye under visible light irradiation. We characterized the prepared samples using various techniques, including XRD, XPS, FTIR, BET, SEM, EDX, TEM, and UV-DRS analyses. Our results indicated that TiO2 and 10%Bi2O3@TiO2 achieved 80% and 100% degradation of EBT dye solution (50 ppm) within 30 min in acidic medium with a 50 mg catalyst dose, respectively. The calcination of the Ti-MOF into TiO2 improved its sensitivity to visible light. The Bi2O3@TiO2 composite was also effective in degrading other organic pollutants, such as Congo Red (degradation ~99%), Malachite Green (degradation ~95%), Methylene Blue (degradation ~81%), and Safranine O (degradation ~69%). The impregnation of Bi2O3 increased the surface acidity of TiO2, enhancing its photocatalytic activity by promoting hydroxyl group formation through increased water adsorption. Additionally, 10%Bi2O3@TiO2 demonstrated excellent chemical stability and reusability, maintaining high degradation efficiency over four cycles. Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations were performed to understand the degradation mechanisms. UV-Vis absorption spectrum simulations suggested that the anionic HEB−2 (O24) or EB−3 forms of the EBT dye are likely to undergo degradation. This study highlights the potential of Bi2O3@TiO2 composites for effective photocatalytic applications in environmental remediation.