A biomimetic imidazole-based hydrogen-bonded organic framework for photoelectrochemical sensing of nerve agent simulants.

Abstract

Inspired by the catalytic triads of lipases that recognize organophosphorus compounds via histidine-imidazole sites, we rationally designed an imidazole-functionalized hydrogen-bonded organic framework (Im-HOF), FDU-HOF-50, as a biomimetic nanozyme for the photoelectrochemical (PEC) sensing of dimethyl chlorophosphate (DCP, a sarin simulant). FDU-HOF-50 features open nanochannels decorated with highly accessible imidazole moieties, creating a confined microenvironment precisely tailored to match the molecular dimensions of DCP. This spatial confinement enables the highly selective capture of the target through a synergistic mechanism of size-exclusion and specific N···P supramolecular interactions. Upon capture, the subsequent hydrolysis-induced protonation of the framework generates imidazolium species, which effectively narrows the band gap of the HOF and dramatically boosts its photoelectric conversion efficiency. Capitalizing on this mechanism, an electrolyte-free, portable photoelectrochemical sensing platform was constructed by integrating the Im-HOF with carbon nanotubes onto interdigitated electrodes. The resulting sensor exhibits an ultra-fast photocurrent response toward DCP, demonstrating a wide linear range of 10-350 ppm, a low detection limit of 2.3 ppm, and superb long-term storage stability (over 30 days). Overall, this work highlights the immense potential of biomimetic imidazole-based HOFs for chemical warfare agent detection, while offering a novel paradigm for engineering enzyme-mimetic framework materials with highly accessible, bio-inspired active sites.