Metal‐based thermally activated delayed fluorescence (TADF) is conceived to inherit the advantages of both phosphorescent metal complexes and purely organic TADF compounds for high‐performance electroluminescence. Herein a panel of new TADF Au(I) emitters has been designed and synthesized by using carbazole and pyrazine‐fused nitrogen‐heterocyclic carbene (NHC) as the donor and acceptor ligands, respectively. Single‐crystal X‐ray structures show linear molecular shape and coplanar arrangement of the donor and acceptor with small dihedral angles of <6.5°. The coplanar orientation and appropriate separation of the HOMO and LUMO in this type of molecules favour the formation of charge‐transfer excited state with appreciable oscillator strength. Together with a minor but essential heavy atom effect of Au ion, the complexes in doped films exhibit highly efficient (Φ∼0.9) and short‐lived (<1 μs) green emissions via TADF. Computational studies on this class of emitters have been performed to decipher the key reverse intersystem crossing (RISC) pathway. In addition to a small energy splitting between the lowest singlet and triplet excited states (ΔEST), the spin‐orbit coupling (SOC) effect is found to be larger at a specific torsion angle between the donor and acceptor planes which favours the RISC process the most. This work provides an alternative molecular design to TADF Au(I) carbene emitters for OLED application.

Aromatic aldehydes are important precursors for pharmaceutical, agricultural, and synthetic chemistry. Compared to thermal catalysis and organic solvent synthesis systems, photocatalytic selective conversion of aromatic alcohol to the corresponding aldehyde coupled with H 2 evolution in pure water represents an alternative due to the mild reaction conditions and the renewable energy production. However, this coupling reaction in aqueous solution is still limited by the low selectivity and conversion due to the over-oxidation. Herein, we demonstrated that the typical type-II heterojunction photocatalysts with a moderate energy band can restrain over-oxidation. This strategy effectively separates the photoexcited charge and hampers the complicated radical oxidation process, thus favoring the generation of aldehyde with the robust evolution of H 2 under visible light illumination without any cocatalyst. The system realizes an anisaldehyde (AA) selectivity of over 99% and a 4-methoxybenzyl alcohol (4-MBA) conversion of over 99% in a low concentration of 4-MBA. Furthermore, when the amount of 4-MBA is expanded to the mL level, the system is able to maintain a robust H 2 evolution rate of 291.8 mmol•g −1 •h −1 at over 99% selectivity for AA. Mechanistic investigation reveals that the photoexcited hole with a moderate potential directly reacts with 4-MBA by promoting the formation of a benzyl carbon radical with abstraction of a hydrogen atom due to the inhibition of •OH formation. Moreover, the effective contact between water, photocatalysts, and 4-MBA also contributes to enhance the conversion activity and improve the practical application potential. The method can be further extended to various aromatic alcohols and offers a concept for highly selective synthesis of high-added value chemicals coupled with H 2 evolution in pure water.