Constructing a 2D Hydrogen-Bonded Organic Framework from Simple Organic Molecules for Efficient Ultralong Room-Temperature Phosphorescence

Although purely organic room-temperature phosphorescence (RTP) materials with long-lived afterglow hold immense potential in optoelectronics, achieving high performance from structurally simple molecules remains a challenge. Herein, we report a novel two-dimensional hydrogen-bonded organic framework (HOF) material, denoted as (H2tbc)n, constructed from the solvent-mediated self-assembly of 1-(4-carboxyphenyl)-1H-1,2,4-triazole-3-carboxylic acid (H2tbc). The resulting (H2tbc)n crystal achieved an exceptional phosphorescence lifetime of 244 ms (λem = 520 nm) under ambient conditions, representing a 122-fold enhancement compared with its molecular precursor. Systematic mechanistic investigations revealed dual confinement mechanisms. The rigid hydrogen-bond framework suppressed high-frequency C–H/N–H vibrational dissipation, thereby reducing nonradiative decay. Concurrently, π···π stacking between the layers enhanced spin–orbit interactions, thereby enabling heavy atom-free intersystem crossing process. This supramolecular approach enables the transformation of a simple molecular building block into an efficient phosphorescent material with long afterglow over 1 s, as demonstrated in a proof-of-concept application for multilevel anticounterfeiting.