Two dimensional iron metal-organic framework nanosheet with peroxidase-mimicking activity for colorimetric detection of hypoxanthine related to shrimp freshness

Two dimensional iron metal-organic framework nanosheet (2D Fe MOF) was facilely synthesized at room temperature by simple stirring of iron salts and terephthalic acid ligand in a mixed solution containing triethylamine. Its morphology and structure were fully characterized by TEM, AFM, XPS and TEM element mapping. Then, its peroxidase-mimicking activity was studied by using H 2 O 2 and 3, 3′, 5, 5′- tetramethylbenzidine as substrate. K m and V max of 2D Fe MOF towards H 2 O 2 were 0.02 mM and 2.08 × 10 −8  M s −1 , respectively. Through the formation of cascade reaction between xanthine oxidase and 2D Fe MOF, a visual method for hypoxanthine (Hx) detection was constructed to evaluate aquatic products freshness. After effective validation, this method presented wide linear range (5.0–500.0 μM), low limit of detection (3.29 μM), satisfied accuracy (recovery of 94.78–99.85%), and good selectivity. By using this method, Hx content in shrimp samples at different storage time were determined.