Cu@MOF core-shell aerogel: High enzyme-like activity for ultratrace colorimetric detection of Hg2+ ions

Abstract

Achieving highly sensitive and selective detection of trace-level heavy metals while maintaining high portability and simplicity remains an intractable challenge. Herein, we report an efficient nanozyme-based colorimetric assay for Hg2+ ion analysis based on a facile design of Cu-based metal@MOF core-shell (Cu@MOF) aerogel. The Cu@MOF aerogel exhibits both aerogel properties (i.e., high porosity and large surface area) and core-shell features (i.e., metal-MOF interfaces). These features largely improve its peroxidase-like activity with a catalytic constant (Kcat) of 4.29×106 s−1, far surpassing the efficiency of both pure Cu aerogel and Cu-MOFs. The superior structure facilitates Hg-triggered amalgam at the metal-MOF interfaces upon exposure to Hg2+ ions, which readily improves the peroxidase-like activity. Consequently, a highly sensitive and selective colorimetric assay has been developed for Hg2+ analysis with a detection range of 10–3000 ng·L−1 and a detection limit as low as 9.33 ng·L−1. Furthermore, high portability and simplicity has been achieved by translating this assay into a flexible and affordable test strip by depositing the as-obtained Cu@MOF aerogel on filter paper. This work not only enables an accurate and convenient analysis of heavy metal ions, but also offers a novel direction for the development of cost-effective nanozyme assays.