Colorimetric assay for the sensitive detection of phosphate in water based on metal–organic framework nanospheres possessing catalytic activity

Abstract

The phosphate content in water is crucial to all forms of life. Excessive phosphate in water can cause the excessive growth of algae and lower the oxygen content in water, which is a danger to our environment. However, most conventional methods for phosphate detection are time-consuming and instrument-dependent. In this work, three Cu-based metal–organic framework nanomaterials (Cu-MOF(1), Cu-MOF(2), Cu-MOF(3)) were synthesized. And it was found that the obtained three nanomaterials all exhibited peroxidase-like activities. Cu-MOF catalyzed color reaction can be inhibited in the presence of phosphate, and a colorimetric assay is constructed for the determination of phosphate by taking Cu-MOF(3) as an example. Good linearity existed between the absorbance of the Cu–MOF/TMB–H₂O₂ system at 652 nm and phosphate concentration from 0.05 μM to 5 μM, with the limit of detection down to 20 nM according to the S/N = 3 rule. Besides, the practicality of our assay was also certified by sensing PO₄³⁻ in local river water samples.