Ordered macro-microporous Co-ZIF nanozyme with phytate enrichment-linker for efficient visual vanillin detection.

Nitrogen-rich zeolitic imidazolate frameworks (ZIFs) are promising for rapid small-molecule sensing due to their tunable porosity. Yet, their practical application is often hindered by mass transfer limitations and low metal utilization caused by intrinsic microporosity. Herein, a hierarchically porous Co-ZIF nanozyme (HP ZIF-67) possessing a three-dimensionally ordered macro-microporous architecture was constructed via in situ crystallization within a 3D ordered hard template using a double-solvent system. Its regularly interconnected macroporous channels and large specific surface area accelerate mass transfer, exposes abundant accessible active sites, and provide confined catalytic environment, leading to remarkably enhanced peroxidase-like activity. Crucially, to facilitate the colorimetric sensing of vanillin (a ubiquitous food additive), phytic acid (PA) was introduced as an enrichment linker to capture vanillin on the HP ZIF-67 surface through cation-bridging. This interaction triggers a pronounced shielding effect on the typical TMB-H2O2 chromogenic reaction, allowing for specific colorimetric recognition of vanillin. The developed sensor, which supports both portable smartphone-assisted digital image readout and accurate absorbance-based measurement, delivers a low detection limit of 0.184 μM across a broad linear range of 2-250 μM, and exhibits good practical utility in real food sample analysis. This work provides a robust and straightforward strategy for flavor quality control and food safety supervision.