Hydrogen‐Bonded Organic Frameworks Enabling Highly Robust Aqueous Phase Ultralong Room‐Temperature Phosphorescence

Abstract Aqueous phase room‐temperature phosphorescence (RTP) materials are attracting increasing interest owing to their unique optical properties and promising applications. However, the realization of ultralong aqueous state RTP remains a formidable challenge due to severe quenching of triplet excitons in aqueous medium. In this study, a universal strategy is presented to achieve aqueous RTP materials through the encapsulation of organic phosphors within rigid hydrogen‐bonded organic frameworks (HOFs) by in situ self‐assembly. Benefiting from the compact and rigid microenvironments provided by HOFs, the nonradiative dissipations are immensely suppressed and populated triplet excitons are greatly stabilized by geometrical confinement and isolating organic phosphors from quenchers. As a result, the assembled HOFs‐based materials reveal robust RTP emission with an ultralong phosphorescence lifetime of up to 493.1 ms and exhibit long‐term optical and structural stability in water and even in harsh conditions (acid and base) for more than 10 days. Moreover, a fluorescent dye is introduced to finely tune the afterglow performance based on triplet‐to‐singlet Förster resonance energy transfer (TS‐FRET), facilitating advanced information encryption and anticounterfeiting applications. This study provides a reliable and universal method to design and prepare robust RTP materials and expands their applications in advanced information encryption.