Tunable Room‐Temperature Phosphorescence in Hydrogen‐Bonded Organic Crystals via H‐Bonding Units

Abstract Organic room‐temperature phosphorescence (RTP) materials with tunable emission colors, lifetime, and quantum yield have important implications for applications in optoelectronics, bioimaging, and anti‐counterfeiting. Herein, a facile strategy is presented for multi‐parameters switchable RTP by introducing second H‐bonding units (SHUs) capable of adsorption and desorption, such as H 2 O and DMSO, into hydrogen‐bonded organic crystals. It is found that the incorporation of H 2 O molecules into the HOC‐PM‐H 2 O structure establishes a robust hydrogen bonding network that stabilizes the triplet excited states, thereby suppressing non‐radiative transitions and extending the phosphorescence lifetime to 904 ± 45 ms. In contrast, DMSO molecules in the HOC‐PM‐DMSO structure promote the separation of aggregate states, leading to a transition in phosphorescence from yellow‐green to blue with a quantum yield of up to 63%. The RTP performance of HOC‐PM‐H 2 O and HOC‐PM‐DMSO can be reversibly switched by SHUs. By leveraging the temporal and spatial changes in lifetime and color, an information security system and afterglow displays activated by SHUs are developed. The SHUs‐activated strategy not only provides a robust platform for revealing structure‐property relationships but also offers a novel approach to designing advanced functional materials with specific luminescent properties.