Bimetallic porphyrin-based covalent organic framework with photo-enhanced oxidase-like activity for colorimetric determination of As(V) in rice samples

<title>Abstract</title> <p> Rapid and sensitive detection of As(V) in rice is of great significance for ensuring food security. Here, a bimetallic porphyrin-based covalent organic framework, Ptp-Fe/Co, was facilely synthesized and characterized by TEM, HRTEM, XRD, EDS mapping, XPS and FT-IR. Notably, its photo-enhanced oxidase-like activity was comprehensively studied. Under light irradiation, Ptp-Fe/Co presented excellent catalytic activity towards TMB with <italic>K</italic> _{<italic>m</italic>} of 0.34 mM and <italic>V</italic> _{<italic>max</italic>} of 2.99×10 ^− 8 M·s ^− 1 . From mechanism study, ·O ₂ ⁻ and ·OH were dominantly produced while its oxidase-like activity was mainly relied on light excitation capability of porphyrin, and cyclic reaction between Fe ³⁺ /Fe ²⁺ and Co ²⁺ /Co ³⁺ . Based on catalytic feature of Ptp-Fe/Co and inhibitory effect of As(V) on acid phosphatase, a colorimetric method for As(V) detection was constructed and verified with broad linear range (7.14–2856.0 µg/L), low LOD (2.35 µg/L), nice reproducibility, satisfactory accuracy and excellent selectivity. Then, it was applied to the detection of As(V) in four parts of rice. </p>