Improving the photocatalytic activity of NH2-UiO-66 by facile modification with Fe(acac)3 complex for photocatalytic water remediation under visible light illumination.

A new and cost-effective photocatalyst was prepared via a facile modification of NH2-UiO-66 with an iron (III) complex i.e. Fe(acac)3, in order to enhance the optical properties and charge separation efficiency of pristine MOF. According to the results of UV-Vis DRS and Tauc plot calculations, the band gap value decreased from 2.7 eV to 2.46 eV for final Fe-UiO-66 photocatalyst, showing the improvement of light absorption in the visible region. Moreover, the photoluminescence (PL) and electrochemical impedance spectroscopies (EIS) confirmed the efficient separation of electron-hole carriers after introduction of Fe(acac)3 into the MOF structure. The photo-Fenton reaction was carried out in the presence of photocatalyst and hydrogen peroxide under white LED illumination for degradation of organic dyes (methyl violet 2B, rhodamine B, malachite green, and methylene blue) and tetracycline (TC) as the examples of water pollutants. A significant dye and TC removal up to 92% and 85% were obtained in photo-Fenton system containing Fe-UiO-66 photocatalyst, respectively. The trap experiment using isopropyl alcohol (IPA) and Na2EDTA demonstrated that the major active species for pollutants degradation are hydroxyl radicals (•OH) and photo-generated holes (h+), respectively. Besides, the transfer of photo-generated electron (e-) to Fe(acac)3 complex resulted in the reduction of Fe3+ to Fe2+ and acceleration of the photo-Fenton reaction. Also, the photocatalyst was found to be very stable during the photo-Fenton reaction according to physicochemical analyses, and it can be reused four times without remarkable decrease in activity.