The fabrication of CuBTC@PW12 with prominent peroxidase-mimicking activity for colorimetric detection of H2O2 and ascorbic acid via “on–off” switch

The Keggin phosphotungstic acid (PW12) embedded metal–organic framework copper benzene-1,3,5-tricarboxylate (CuBTC), CuBTC@PW12, was fabricated by a facile hydrothermal synthesis technique. With a unique tetrakaidecahedron structure and multiple active sites, the obtained CuBTC@PW12 exhibited peroxidase-mimicking activity, which promoted a novel strategy for qualitative and quantitative detection of hydrogen peroxide (H2O2) and sequential sensing of ascorbic acid (AA) via colorimetric evolution. Notably, with the advantages of strong redox performance of POMs and the unique porous structure of metal organic frameworks (MOFs), as peroxidase mimics, CuBTC@PW12 achieved highly selective and sensitive detection of H2O2via oxidizing TMB to a blue oxidation product (ox-TMB), with a limit of detection of 2.67 μM within the 0.01 to 1.0 mM scale. Concomitantly, the AA can be monitored consecutively by reducing the ox-TMB with fading blue color quantitatively with a limit of detection at 0.15 μM in the range of 0.01–0.10 μM. The recoveries for the determination of AA in human serum were obtained at 94.63–105%. These results manifested that CuBTC@PW12 could be used as a peroxide-mimetic enzyme for the continuous detection of H2O2 and AA with the advantages of simplicity, efficiency, sensitivity and accuracy.