Colorimetric detection of thiocyanate via inhibiting the peroxidase-like activity of Fe-modified porphyrinic metal-organic framework

Abstract

Monitoring thiocyanate (SCN⁻) levels is important for both food safety and the health of humans. In this study, a colorimetric strategy based on Fe-modified porphyrinic MOF (PCN-224-Fe) for SCN⁻ detection was developed. The insertion of Fe³⁺ to PCN-224 leads to the formation of Fe–N₄ structure and endows the nanoprobe with peroxidase-like activity, and colorless TMB is oxidized to blue oxTMB in the presence of H₂O₂. Based on the formation of Fe(SCN)₆³⁻, SCN⁻ can poison the active Fe–N₄ site, thus inhibiting the peroxidase-like activity of the sensor. The colorimetric linear concentration-response of PCN-224-Fe towards SCN⁻ is 0.1–1 μM and 1–20 μM with a limit detection of 44 nM and 0.41 μM, respectively. This approach has shown its sensing accuracy of SCN⁻ in milk and human urine samples with recoveries ranging from 96.49 % to 102.79 %, proving its practical application in real samples analysis.