Reconstructing hydrophobic ZIF-8 crystal into hydrophilic hierarchically-porous nanoflowers as catalyst carrier for nonenzymatic glucose sensing

Abstract

ZIF-8, a zeolite-type metal-organic framework (MOF), is an effective carrier to support nanocatalysts for applications in the catalysis areas due to its high chemical and thermal stability, and unique structure. The ability to reconstruct the structure of ZIF-8 opens up the potential to enhance its performance in catalysis. In this work, the structure of hydrophobic ZIF-8 crystal is engineered to form hydrophilic hierarchically-porous nanoflowers (HHNs) by using an organic weak acid as etchant. Results reveal that besides imparting hydrophilicity to ZIF-8, the uniform micropores in ZIFs are transformed to mesopores and macropores, which are beneficial to nanoparticle immobilization and electrochemical reactions. After incorporating Cu nanoparticles into the matrix HHNs, the composite Cu@HHNs manifest superior catalytic activities for glucose electro-catalytic oxidation under alkaline media, compared with Cu nanoparticles loaded on untreated ZIF-8. The proposed Cu@HHNs based sensor displays exceptional sensing performances with a linear range of 5 μM to 3 mM, a detection limit of 1.97 μM (signal-to-noise ratio (S/N) of 3), a sensitivity of 1594.2 μA mM−1 cm−2, and high selectivity, specificity, and reproducibility. In addition, Cu@HHNs can be utilized for glucose sensing in human blood serum, demonstrating its feasibility toward determination of glucose for practical sample testing.