Zero-Valent Iron/TiO₂ Supported on MOF Aerogel for Photo-Fenton Degradation of Trichloroacetic Acid

To address the limitations of conventional remediation techniques and fully harness the synergistic potential of advanced oxidation processes (AOPs), this study developed a novel photocatalytic system, TiO₂/MOF-808@SiO₂@Fe(0), for the efficient degradation of trichloroacetic acid (TCA) under UV irradiation. The composite catalyst was synthesized via a multi-step procedure: first, a hierarchically porous SiO₂ aerogel support was prepared by the sol-gel method; next, MOF-808 nanocrystals were grown in situ within the aerogel matrix; then, UV-responsive TiO₂ nanoparticles were deposited; and finally, zero-valent iron (Fe(0)) was immobilized to activate the photo-Fenton pathway. This composite architecture combines the high specific surface area and structural stability of the SiO₂ aerogel, the adsorptive porosity of MOF-808, the photocatalytic efficiency of TiO₂, and the reductive capacity of zero-valent iron. Experimental results show that at pH 6 and 45 °C, using 50 mL of 10 mg/L TCA solution, the system achieved a high TCA degradation rate of approximately 94.2%. This high performance is attributed to synergistic interactions among Fe²⁺, Fe(0), and TiO₂, which together enable efficient TCA mineralization. The system thus represents a novel and promising technological platform for the removal of recalcitrant organochlorine compounds in water treatment.