Abstract

• Metal nanoparticles (Pt, Pd and Ag) were deposited on NH 2 -MIL-125. • Pt/NH 2 -MIL-125 achieves the best acetaminophen degradation. • Superoxide radicals are the main reactive oxygen species. • Pt/NH 2 -MIL-125 maintains its structure after three successive cycles. This work reports the solvothermal synthesis of a titanium-based metal organic framework (NH 2 -MIL-125(Ti)) and the further deposition of palladium, platinum and silver nanoparticles on its framework, with the aim to obtain visible light-driven photocatalysts. The structure of the NH 2 -MIL-125 was not affected by the incorporation of the metal nanoparticles, while the textural properties changed depending on the metal used. All M/NH 2 -MIL-125 (M = Pd, Pt, Ag) synthesized materials showed enhanced light absorption in the visible region due to the effect of the metal nanoparticles, which were mainly in reduced state as confirmed by XPS analyses. The metal nanoparticles were between 1.8 and 3.8 nm in size depending of the metal. They were responsible for the reduction in the recombination process, as suggested by photoluminescence measurements. The photocatalytic performance of M/NH 2 -MIL-125 was tested for the degradation of acetaminophen (ACE) under simulated solar irradiation. Pt/NH 2 -MIL-125 achieved the highest conversion rate (rate constant of 0.0165 min −1 ), with complete conversion of the contaminant in less than three hours. Scavengers studies confirmed that O 2 − radicals play a main role in the degradation process, followed by OH radicals. The catalytic stability of Pt/NH 2 -MIL-125 was confirmed upon three successive reaction cycles. Different water matrices were tested to understand the effect of common inorganic ions, being the presence of bicarbonates the most detrimental to the performance of the photocatalytic process.

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