Dye sensitized photocatalytic degradation of congo red and rhodamine B by 1,3,5-Benzenetricarboxylic acid based metal organic frameworks Ni3(BTC)2.12H2O, (Ni0.8Co0.2)3(BTC)2.12H2O and Cu3(BTC)2 under visible light

Abstract

Photocatalytic degradation is a promising approach for the removal of organic pollutants from wastewater. This study explores the efficiency of three metal-organic frameworks (MOFs)—Ni₃(BTC)₂•12H₂O, (Ni₀.₈Co₀.₂)₃(BTC)₂•12H₂O, and Cu₃(BTC)₂—in degrading Congo Red and Rhodamine B dyes under visible light. The MOFs were synthesized via a solvothermal method using 1,3,5-benzenetricarboxylic acid (BTC) as the organic ligand. Their structures were thoroughly characterized through various techniques, including PXRD, FE-SEM, EDX, HRTEM, FT-IR, Raman spectroscopy, TGA, and BET analysis. Despite their band gap energies exceeding 3 eV, which limits direct visible light absorption, the photocatalytic degradation was successful, suggesting a dye-sensitized mechanism. Among the MOFs, Cu₃(BTC)₂ exhibited the highest degradation efficiency, achieving 99.99 % Congo Red degradation in 20 min and 5 % Rhodamine B degradation in 25 min. Optimal degradation for both dyes occurred at pH 5. The catalyst's stability was confirmed through a recyclability test across four successive cycles. The exceptional performance of Cu₃(BTC)₂ is attributed to its large surface area (1064 m²g⁻¹). The incorporation of cobalt into the (Ni₀.₈Co₀.₂)₃(BTC)₂ framework enhanced the degradation rates compared to pure Ni₃(BTC)₂. These findings underscore the potential of MOFs as effective photocatalysts for environmental remediation under visible light, offering a promising avenue for wastewater treatment.