Target-induced mimic enzyme deactivation based on mixed-node metal-organic frameworks for colorimetric assay of hydrogen sulfide

Accurate detection of hydrogen sulfide (H₂S) is of great significance for environmental monitoring and protection. We propose a colorimetric method for the detection of H₂S by the use of mixed-node Cu-Fe metal organic frameworks (Cu-Fe MOFs) as highly efficient mimic enzymes for target-induced deactivation. The Cu-Fe MOFs were synthesized by a simple solvothermal method and could catalyze the H₂O₂ mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxTMB with a blue color. The presence of dissolved H₂S would deactivate the mimic enzymes, and then the blue color disappeared. The mechanism of the sensor was discussed by steady-state kinetic analysis. The designed assay was highly sensitive for H₂S detection with a linear range of 0−80 μmol/L and a detection limit of 1.6 μmol/L. Moreover, some potential substances in the water samples had no interference. This method with the advantages of low cost, high sensitivity, selectivity, and visual readout with the naked eye was successfully applied to the determination of H₂S in industrial wastewater samples.