Tunable Photoluminescent and Photothermal Properties of Organic Cocrystals Containing Hydrogen‐Bonded Interlocked Planar Molecules

Engineering intramolecular hydrogen‐bonded planar architectures provides a versatile strategy for modulating the photoluminescent and photothermal behaviors of organic cocrystals. This work not only overcomes the limitations of selecting conjugated (hetero)aromatic compounds to meet the requirements of planarity and rigidity for cocrystal precursors, but also bridges the gap between monomer and their cocrystals. Abstract Expanding the structural diversity of precursor molecules can inject greater vitality into the development of cocrystal engineering. Here, two hydrogen‐bond interlocked planar molecules, HNAO and HPAO is reported, which coassemble with 1,2,4,5‐tetracyanobenzene (TCB) into charge‐transfer (CT) cocrystals NTC and PTC. The resulting NTC inherits two‐photon adsorption properties from HNAO, with the bathochromic shift enhanced by synergistic ESIPT and CT interactions, ultimately achieving near‐infrared emission. Remarkably, the intramolecular hydrogen bonds lock the molecule into a planar and ordered conformation, enabling regular face‐to‐face packing in NTC organic microwires and yielding the lowest optical‐loss coefficient (0.021 dB/µm) of organic cocrystal to date, thereby demonstrating great potential for applications in optical computing systems. In contrast, the extremely low energy gap between the HOMO of HPAO and the LUMO of TCB in PTC drives a dramatically higher degree of CT in its excited states, predominantly facilitating non‐radiative transitions and resulting in non‐emissive behavior. Nevertheless, this trade‐off enables efficient NIR‐I photothermal conversion (η = 47.7%) and excellent photostability, making PTC highly effective for rapid photothermal imaging and breakthrough time‐dependent information encryption applications. This work enriches the library of cocrystals and provides a novel strategy for tailoring the properties of cocrystal materials. Engineering intramolecular hydrogen-bonded planar architectures provides a versatile strategy for modulating the photoluminescent and photothermal behaviors of organic cocrystals. This work not only overcomes the limitations of selecting conjugated (hetero)aromatic compounds to meet the requirements of planarity and rigidity for cocrystal precursors, but also bridges the gap between monomer and their cocrystals. Abstract Expanding the structural diversity of precursor molecules can inject greater vitality into the development of cocrystal engineering. Here, two hydrogen-bond interlocked planar molecules, HNAO and HPAO is reported, which coassemble with 1,2,4,5-tetracyanobenzene (TCB) into charge-transfer (CT) cocrystals NTC and PTC. The resulting NTC inherits two-photon adsorption properties from HNAO, with the bathochromic shift enhanced by synergistic ESIPT and CT interactions, ultimately achieving near-infrared emission. Remarkably, the intramolecular hydrogen bonds lock the molecule into a planar and ordered conformation, enabling regular face-to-face packing in NTC organic microwires and yielding the lowest optical-loss coefficient (0.021 dB/µm) of organic cocrystal to date, thereby demonstrating great potential for applications in optical computing systems. In contrast, the extremely low energy gap between the HOMO of HPAO and the LUMO of TCB in PTC drives a dramatically higher degree of CT in its excited states, predominantly facilitating non-radiative transitions and resulting in non-emissive behavior. Nevertheless, this trade-off enables efficient NIR-I photothermal conversion (η = 47.7%) and excellent photostability, making PTC highly effective for rapid photothermal imaging and breakthrough time-dependent information encryption applications. This work enriches the library of cocrystals and provides a novel strategy for tailoring the properties of cocrystal materials. Advanced Science, Volume 12, Issue 48, December 29, 2025.