Highly stable UiO-66-NH2 by the microwave-assisted synthesis for solar photocatalytic water treatment

This work introduces the novel use of a highly stable UiO-66-NH2 in water with a linker release less than 0.2‰ (per-mile) in a wide pH range. The MOF was prepared by a fast microwave-assisted method comparing for the first time the effect of two Zr precursors: Zr oxychloride and organic Zr alkoxide; with synthesis temperatures 120–180 ºC. The use of oxychloride as Zr precursor led to a MOF with bigger particle and crystal size than the Zr alkoxide. The sample prepared with ZrOCl2 at 140 ºC resulted in the best crystallinity, highest textural definition (area 875 m2 g−1, pore volume 0.39 cm3 g−1), good optical properties for solar radiation absorption (bandgap 2.88 eV), and the highest photoactivity to remove sulfamethoxazole in water. The activity of the optimum UiO-66-NH2 sample was assessed in a continuous flow experiment, testing the ability of the simultaneous degradation of a six pharmaceutical mixture fed at a more realistic environmental scenario (500 μg L−1 each). The MOF showed an outstanding stability over 20 h with no detectable release of linker and high removal efficiencyRafael Rodríguez Solís is grateful to the Spanish Ministry of Science, Innovation and Universities for his postdoctoral contract (Juan de la Cierva Formación, Ref. FJC2018-035513-I). Manuel Peñas Garzón acknowledges the Spanish Ministry of Education, Culture and Sports for his predoctoral contract (Ref. FPU16/00576) contracts. This research was funded by the Spanish State Research Agency (PID2019-106186RB-100/AEI/10.13039/501100011033, Spain). The authors are also grateful to the supporting analyses provided by the external services of the Autonomous University of Madrid (SIdI), University of Extremadura (SAIUEx), University of Zaragoza (SAI), University of Málaga (SCAI) and Universidad Complutense of Madrid (CAI