Fluorescent hydrogen-bonded organic framework act as a multifunctional platform for Fe and F sensing, and for information encryption.

Due to their exceptional optical properties and adjustable functional characteristics, hydrogen-bonded organic frameworks (HOFs) demonstrate significant potential in applications such as sensing, information encryption. However, studies on the synthesis of HOFs designed to construct multifunctional platforms are scant. In this work, we report the synthesis of a new fluorescent HOF by assembling melem and isophthalic acid (IPA), designated as HOF-IPA. HOF-IPA exhibited good selectivity and sensitivity towards Fe, making it suitable as a fluorescent sensor for Fe detection. The sensor achieved satisfactory recoveries ranging from 97.79 % to106.42 % for Fe sensing, with a low relative standard deviation (RSD) of less than 3.33 %, indicating significant application potential for HOF-IPA. Due to the ability of F to mask the electrostatic action on the surface of Fe and inhibit the photoelectron transfer (PET) of HOF-IPA, the HOF-IPA - Fe system can be utilized as a fluorescent "off-on" sensor for F detection. Additionally, owing to the colorless, transparent property of HOF-IPA in aqueous solution under sunlight and its blue fluorescence property under UV light (color) or microplate reader (fluorescence intensity), HOF-IPA based ink can be used for various types of information encryption, and all yielding favorable outcomes.