Linker-modulated copper-based covalent organic frameworks for integrated nitrophenol reduction and fluorescence sensing

Metal-cluster-based covalent organic frameworks (MCOFs), which combine robust covalent skeletons with accessible metal centers, are highly promising platforms for multifunctional catalysis and sensing. However, how framework structure and functional binding sites collectively govern catalytic and sensing performance remains insufficiently understood. Herein, two copper-cluster-based covalent organic frameworks (Tapt-Cu 3 and Tapyt-Cu 3 ) were synthesized based on a Cu 3 L 3 cluster and triazine-based amine linkers. Both frameworks exhibited high crystallinity, structural stability, and reusable catalytic and fluorescence sensing performance toward nitrophenols. Tapyt-Cu 3 showed superior catalytic performance, achieving 99.9% conversion of p-nitrophenol within 5 min. The reduction followed apparent pseudo-first-order kinetics. Comparative H 2 evolution and EIS measurements suggest that the enhanced catalytic activity of Tapyt-Cu 3 is associated with a greater apparent ability to promote BH 4 − hydrolysis/oxidation and more favorable interfacial charge transport. Both frameworks also selectively detected nitrophenols through fluorescence quenching, with Tapyt-Cu 3 producing stronger responses and a detection limit of 0.81 μM for 2,4,6-trinitrophenol. The quenching process was governed primarily by competitive absorption and photoinduced electron transfer, with static quenching predominating. The pyridyl-containing and nitrogen-rich environment of Tapyt-Cu 3 provides potential sites for short-range interactions with nitrophenols and may facilitate interfacial charge transfer, thereby enhancing its performance in sensing and catalytic systems. The results establish clear relationships among linker modulation, molecular recognition, charge transfer, and multifunctional performance. This study demonstrates that rational modulation of framework structure and binding environments can simultaneously improve nitrophenol conversion and detection, providing a useful strategy for designing multifunctional MCOFs for environmental remediation and pollutant monitoring.