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 efficiency.