Design and transformation of ACQphores into AIEgens: toward MOF-based advanced sensing applications

Aggregation-induced emission (AIE) has emerged as a groundbreaking optoelectronic phenomenon that overcomes the limitations of aggregation-caused quenching (ACQ), enabling the development of highly light-emitting substances with broad applications. This overview presents a detailed exploration of AIE and ACQ, discussing their historical background, fundamental definitions, and working mechanisms, particularly the restriction of intramolecular rotations (RIRs), vibrations (RIVs), and motions (RIMs). Significant focus is placed on the transformation strategies for converting ACQ-active fluorophores (ACQphores) into AIE-active luminogens (AIEgens). Beyond molecular design, this review delves into the rapidly expanding field of AIE-based metal-organic frameworks (AIE-MOFs) and their utilization in sensing. Various AIE-MOF systems developed for the sensing of biological molecules, volatile organic compounds (VOCs), heterocyclic compounds, and nitroaromatic explosives are discussed, demonstrating their exceptional sensitivity, selectivity, and stability. Additionally, stimuli-responsive luminescent materials capable of detecting changes in temperature, pressure, and pH are discussed, showcasing their potential for dynamic environmental sensing. Overall, this review highlights the synergy between AIE and MOF chemistry, with a distinct emphasis on the mechanistic transformation of ACQphores into AIEgens and their structural influence on emissive behaviour. Unlike broader reviews, this article is specifically organized around the sensing applications of AIE-MOFs, classifying them by analyte type and thereby exploring multifunctional AIE-MOF platforms for advanced sensing and imaging applications.