Heterojunction Engineering of POMOF and ZnO: A Promising Strategy to Boost Triethylamine Gas-Sensing Performance for Fish Freshness Evaluation

Abstract Triethylamine (TEA) serves as a key indicator of fish spoilage, and its accurate detection is essential for assessing fish freshness. However, existing TEA gas sensors often suffer from low sensitivity, sluggish response/recovery kinetics, and high operating temperatures. To address these limitations, this study, for the first time, integrates polyoxometalate-based metal–organic frameworks (POMOF) with ZnO via heterojunction engineering to construct a POMOF-ZnO heterojunction gas sensor. At an operating temperature of 140 °C, the sensor exhibits outstanding performance toward 10 ppm TEA, including a high response value (64.54), fast response/recovery times (49/108 s), excellent selectivity, and good long-term stability over 32 days. Material characterization reveals that the heterojunction formed between POMOF and ZnO significantly increases the number of active sites on the material surface. Furthermore, combining density functional theory (DFT) calculations, current–voltage (I–V) measurements, and in-situ Fourier transform infrared (FTIR) analysis, the underlying gas-sensing mechanism is systematically and comprehensively discussed. The practical applicability of the sensor is demonstrated by its successful detection of TEA released from crucian carp during room-temperature storage, highlighting its potential for rapid assessment of fish freshness. This work presents a novel approach for designing high-performance gas sensors based on POMOF-ZnO heterojunctions for fish freshness evaluation.