Amorphous copper(II)-cyanoimidazole frameworks as peroxidase mimics for hydrogen sulfide assay.

Metal-organic frameworks with hierarchical porosities and exposed active sites are promising for ideal enzyme mimics. In this work, we developed a simple and feasible air oxidation strategy to prepare amorphous Cu(II)-cyanoimidazole frameworks (aCu(II)-CIFs) using CuI as the metal source in dimethylsulfoxide. Benefiting from coordination unsaturation and hierarchical porosities, aCu(II)-CIFs exhibit inherent peroxidase-mimic activity for rapid colorimetric reaction of 3,3',5,5'-tetramethylbenzidine (TMB). aCu(II)-CIFs were utilized to develop a colorimetric platform for specific H2S assay in the range of 0.6-30 μM, achieving a limit of detection (LOD) of 0.071 μM. Structural collapse of aCu(II)-CIFs and subsequent generation of stable CuS particles, along with reducibility of H2S, are likely responsible for suppressing TMBox conversion. The proposed method successfully detected H2S in real water samples, with a relative standard deviation (RSD) lower than 8.4%. This contribution is expected to offer unique insights into the amorphization mechanisms of MOFs and their potential applications.