# Water-Promoted Molar-Level Photocatalysis and Spontaneous Product Separation with Near-Unity Quantum Efficiency.
> 水添加による光触媒的アミン脱水素縮合反応の促進と自発的生成物分離の実現


## Abstract

This study demonstrates that introducing water into photocatalytic systems markedly accelerates the dehydrogenative condensation of amines, enabling imine synthesis at high substrate concentrations without organic solvents. Two mechanistic roles of water were identified: reduction of the adsorption energy of generated hydrogen atoms to promote H2 liberation, and steering of the benzimine intermediate conversion through an energetically favorable pathway. Using a Ru/TiO2 photocatalyst, complete conversion of 20 vol% (1.9 M) benzylamine was achieved at a 100 mL scale with an average quantum efficiency (QE) of 20%, yielding approximately 20 g of benzylidenebenzylamine via spontaneous phase separation. A Rh/TiO2 photocatalyst further raised the QE to near unity at 70 vol% (6.7 M) benzylamine. The approach showed broad substrate compatibility, excellent scalability, and minimal purification requirements, offering a practical and sustainable route for selective chemical synthesis.

### Mechanism

Water reduces the adsorption energy of photogenerated hydrogen atoms on the catalyst surface, facilitating H2 desorption, while simultaneously directing the benzimine intermediate through a lower-energy conversion pathway, collectively enhancing overall photocatalytic quantum efficiency.

## Bibliographic

- **Authors**: Lu Y, Luo R, Leng X, Huang Y, Jiang W, Besenbacher F, et al.
- **Journal**: J Am Chem Soc
- **Year**: 2025 (2025-12-10)
- **PMID**: [41287352](https://pubmed.ncbi.nlm.nih.gov/41287352/)
- **DOI**: [10.1021/jacs.5c15003](https://doi.org/10.1021/jacs.5c15003)
- **Study type**: in vitro study
- **Delivery route**: in vitro
- **Effect reported**: not assessed

## Delivery context

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

## Safety notes

This is basic research at the cellular or molecular level. For human application, inhalation is the most promising delivery route, but inhalation carries explosion risk and concentration matters (empirical LFL of 10%; high-concentration devices are not recommended).

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 41287352. https://h2-papers.org/en/papers/41287352
> **Source**: PubMed PMID [41287352](https://pubmed.ncbi.nlm.nih.gov/41287352/)