Synergistic Aggregation-Induced Emissive Linkers in Metal–Organic Frameworks for Ultrasensitive and Quantitative Visual Sensing

Luminescent metal-organic frameworks (MOFs) represent an emerging class of materials for visual analyte detection. In this study, we present a strategy that integrates two synergistic aggregation-induced emissive (AIE) linkers into a MOF, significantly enhancing sensing sensitivity, selectivity, and quantification capabilities for practical applications. The dual AIE linkers simultaneously optimize porosity and amplify emission intensity. The tailored pore structure precisely matches the molecular dimensions of the pesticide 2,6-dichloro-4-nitroaniline (DCN), while Förster resonance energy transfer between the linkers achieves an exceptional fluorescence quantum yield of 92.6%. This design enables ultrasensitive DCN detection in water, with an unprecedented detection limit at the ppb level, along with superior selectivity, rapid response time, high quantification accuracy, recyclability, and strong resistance to interference. A comprehensive investigation using UV-vis, fluorescence, transient absorption, X-ray photoelectron, and Raman spectroscopies, supported by theoretical calculations, attributes the efficient fluorescence quenching to photoinduced energy transfer. Additionally, we demonstrate instant, naked-eye detection of DCN residues on fruit surfaces and contaminated soil by applying MOF solutions and illuminating under UV light. Quantitative analysis of DCN residues on fruits was further achieved using computer vision and a custom script, providing a practical, on-site method for rapid and precise detection of pesticide residues.