Single-Molecule-Like Intramolecular Charge Transfer in Multi-Nitrogen Hybridization HOF for Highly Selective Water Detection

Abstract

Luminescent organic crystals have attracted significant attention due to their potential in sensing and anti-counterfeiting, yet organic molecules frequently adopt a strong aggregation tendency with dense stacking and short intermolecular distances, leading to a barrier for the dynamic signal output of single molecule. Herein, we report the single-molecule-like dynamic emission from a low-aggregated hydrogen-bonded organic framework (HOF) system via a multi-nitrogen hybridization strategy. A HOF with donor-acceptor structure was designed via hybridizing the nitrogen atoms into both the aromatic backbone and the hydrogen-bond acceptor. The designed HOF permits the exposure of nitrogen-based recognition sites in channels, which easily triggers the charge interactions with external solvent molecules, especially water molecules, resulting in polarity-regulated intramolecular charge transfer (ICT) process, akin to that of single building block. On this basis, this HOF system holds the highly selective water-responsive emission behavior, which can effectively identify the trace water in the air, further serving as a humidity-controlled anti-counterfeiting platform. These results present a promising strategy for constructing dynamic single-molecule-like emission systems tailored for highly efficient anti-counterfeiting.