Preparation of NH2-UiO-66 NPs
ZrCl4 (0.48 g), 2-aminoterephthalic acid (NH2-BDC, 0.37 g), and deionized water (11.9 μL) were added in N,N-dimethylformamide (DMF, 40.0 mL) and dissolved by stirring and ultrasonic treatment.44 The transparent precursor was transferred into a Teflon-lined stainless-steel autoclave. For crystallization, the autoclave was thermally treated at 120 °C for 24 h. After natural cooling to room temperature, the formed powders were isolated by centrifugation at 6000 rpm for 6 min. Eventually, the obtained powders were washed by DMF and methanol for several times, and dried in vacuum at 100 °C overnight.