Water‐Enabled Ultralong Full‐Color Organic Phosphorescence in Hydrogen‐Bonded Frameworks for 4D Encryption and Bio‐Imaging

Developing water-stable organic room-temperature phosphorescence (RTP) materials remains a formidable challenge due to water-induced quenching. Herein, we present a counter-intuitive strategy to achieve water-enhanced ultralong RTP via the in situ encapsulation of carbonyl-based guests within a rigid hydrogen-bonded organic framework (HOF). Unlike conventional systems where water acts as a quencher, we demonstrate that water molecules function as pivotal structural reinforcers. Mechanistic studies reveal that water bridges host-guest hydrogen-bonding sites, constructing a denser network that rigidifies molecular conformation and promotes intersystem crossing. Consequently, phosphorescence intensity peaks at a high water content of 55 wt.%. Significantly, this universal strategy enables full-color ultralong phosphorescence (from blue to deep red) by tuning guest conjugation-a rare feat in aqueous media. Benefiting from exceptional physiological stability and biocompatibility, these nano-sized hybrids overcome intracellular quenching bottlenecks, enabling high-signal-to-noise ratio cellular bio-imaging. Additionally, applications in 4D encryption and humidity sensing are demonstrated. This work transforms a traditional phosphorescence killer into a synergistic enhancer, offering a novel paradigm for designing high-performance RTP materials tailored for biological applications.