Structural Water Synergistic Hydrogen-Bonded Organic Frameworks: A Fluorescent Sensing Platform Oriented for Intelligent Accessibility

Abstract

Using 1,3,5-Tris(4-aminophenyl)benzene (TAPB) as the precursor, we synthesized two single-crystal hydrogen-bonded organic frameworks (HOFs-T and HOFs-TW). We systematically investigated the impact of reaction conditions on their structural properties and assessed their potential as optical sensing materials. In our experiments, HOFs-TW unexpectedly showed a hexagonal tubular morphology with a stable snowflake-shaped structural water. These water molecules and TAPB monomers form an ordered hydrogen-bonding network that reduces aromatic ring dihedral angles, induces coplanarization, and significantly enhances HOF-TW's charge-transfer and photon conversion efficiency (quantum yield 66.56%). Utilizing the optical properties of HOFs-TW, we incorporated green carbon quantum dots (CDs) and used molecularly imprinted polymers (MIPs) as the selective component to develop a ratiometric fluorescence sensor (CDs@SiO₂/HOFs-TW@MIPs). This sensor was designed for the detection of clofibric acid (CLF) in environmental samples, exhibiting a linear range of 0-360 μM and a detection limit of 0.1775 μM. Additionally, we prepared the corresponding fluorescence test papers and independently developed a smartphone-based fluorescence-colorimetric sensing application. The test paper's fluorescence stabilizes within 1 min 20 s, with three parallel measurements via an app (relative error 0.205%), completed within 3 min. This study provides significant theoretical support and insights into the design and morphological control of single-crystal HOFs. We envision that this work will further advance the application of fluorescence rapid detection and optical sensing, expanding its applicability for real-time monitoring in various scenarios.