Biomimetic recognition–catalysis coupled paper sensor for smartphone-based colorimetric detection of linalool in tea

Linalool, a key monoterpene volatile organic compound, plays a vital role in plant stress signaling and agricultural quality evaluation. Herein, we developed a portable sensing platform by integrating molecularly imprinted metal–organic framework nanozymes (MIP@His-MOF) with smartphone-assisted colorimetric analysis. Histidine-functionalized MIL-101 was designed to mimic the catalytic environment of horseradish peroxidase, while molecular imprinting introduced selective recognition sites for linalool. This dual-functional design led to a 3.9-fold increase in catalytic efficiency and significantly improved selectivity. The optimized sensor achieved a limit of detection of 0.14 ppm in solution and retained high sensitivity in a paper-based format (0.62 ppm). As a proof of concept, the paper sensor successfully differentiated black tea quality grades, showing strong correlation with GC–MS results. This work highlights a modular, low-cost, and field-deployable approach for volatile compound detection in precision agriculture and food quality monitoring.