Hollow-Structured CNQDs@CTP Z-Scheme Heterojunctions for the Construction of a PEC Sensing Platform: High-Sensitivity Detection of PFOA in Water

Perfluorooctanoic acid (PFOA) is an emerging environmental pollutant due to its high bioaccumulation, toxicity, environmental persistence, and widespread presence. Its detection is crucial for assessing water quality safety. In this study, a molecularly imprinted photoelectrochemical (MIP-PEC) sensor based on a Z-scheme heterojunction of covalent organic framework–confined graphitic carbon nitride quantum dots (CNQDs@CTP) was developed for the highly sensitive and selective detection of PFOA in water. First, the novel CNQDs@CTP composite was prepared via a self-templating method, which featured a unique hollow structure. The hollow structure and Z-scheme heterojunction significantly improved light absorption and carrier separation efficiency, with an electron lifetime reaching 6.72 × 10–2 s and high incident photon-to-electron conversion efficiency (IPCE). Furthermore, when combined with molecularly imprinted technology, PFOA-specific recognition sites were constructed on the electrode surface, yielding an imprint factor of 9.3. Under optimized conditions, the sensors had a wide detection range (1.00 × 10–11 to 5.00 × 10–6 mol·L–1) and a low detection limit (5.50 × 10–12 mol·L–1). The water sample detection results were highly consistent with the LC-MS/MS results. The sensors combined high sensitivity, low cost, and ease of operation, providing an innovative solution for the accurate and sensitive detection of PFOA in water.