A portable functionalized multi-emissive MOF-based thin-film sensor (OPA-MEMOF@PVA) was developed for the rapid, sensitive, and selective detection of NH₄⁺-N. The sensor was fabricated by first modifying 4-bromophthalaldehyde (OPA) onto a multi-emissive metal-organic framework (MEMOF), followed by blending with polyvinyl alcohol (PVA). Under optimized conditions, the thin-film sensor exhibited excellent NH₄⁺-N detection performance, achieving a low limit of detection (LOD) of 69.2 nM and a response time of 3 min. Furthermore, OPA-MEMOF@PVA manifested outstanding selectivity and robust anti-interference ability towards NH₄⁺-N. The enhanced detection performance is most consistent with the effective adsorption and enrichment of NH₄⁺-N by the functionalized MOF, combined with a specific interaction between the dialdehyde groups of OPA-MEMOF and NH₄⁺-N. When applied to real groundwater samples, the thin-film sensor demonstrated satisfactory recoveries (97–103%) with a relative standard deviation (RSD) of less than 3%. Owing to its rapid response, portability, and high selectivity, OPA-MEMOF@PVA shows great promise as a reliable sensing platform for on-site NH₄⁺-N detection.
He et al. (Thu,) studied this question.