Hydrogenation reactions are fundamental in the fine chemical, pharmaceutical, and petrochemical industries, however heavily relying on H2 gas at high temperatures and pressures, incurring large energy and carbon costs. Photocatalytic transfer hydrogenation, using water as a proton source, offers a greener alternative, but existing photocatalysts often suffer from modest yields, limited selectivity, and narrow substrate scope. Additionally, they often require co-activation, such as Mg-activated water or non-sustainable hydrogen feeds. Here, a photocatalyst is introduced that offers high yields and selectivities across a broad spectrum of organic compounds. The developed photocatalyst is a multivalence palladium superstructure with ultrasmall Pd0 nanoparticles enveloped by isolated Pd2+/Pd4+ atoms within a carbon-nitride matrix. Mechanistic studies reveal that the redox-flexible Pd single atoms, with triethylamine as an electronic modulator, attract photogenerated holes for water oxidation, while Pd0 nanoparticles facilitate hydrogen transfer to the unsaturated bonds of the organic molecules. The cooperative and dynamic behavior of Pd centers during catalysis, involving transitions among Pd+2, Pd+3, and Pd+4 states, is validated using operando electron paramagnetic resonance spectroscopy. This multivalent palladium catalyst represents a conceptual advance in photocatalytic transfer hydrogenation with water as a hydrogen source, holding promise for sustainable hydrogenation processes in the chemical industry.

• Keywords
• carbon nitride, hydride transfer, palladium, photocatalysis, selective hydrogenation,
• Publication type
• Journal Article MeSH

Climate change and the depletion of fossil fuels increase the demand for sustainable energy. Biodiesel synthesized using heterogeneous acid catalysts is a promising clean-energy carrier that supports a circular carbon economy. Herein, the efficient synthesis of biodiesel is reported using a reusable solid acid graphene catalyst functionalized with a natural aminosulfonic acid. Experimental and theoretical studies reveal the key role of functionalities that simultaneously contain amino and sulfonate groups, which impart superior acidity. Excellent activity and selectivity for oleic acid conversion to oleic acid methyl esters (a sustainable biofuel) are obtained, offering a strategy for achieving improved catalytic performance compared to earlier or benchmark catalysts in the field. Notably, the catalyst also effectively converts common vegetable oils into biodiesel via transesterification and facilitates carbohydrate dehydration to value-added chemicals, demonstrating broad applicability. Two additional variants of aminosulfonic acid-functionalized graphene show similar activity, confirming the crucial role of these functionalities in achieving high acidity and catalytic performance. The development of such potent, recyclable catalysts is crucial because acid catalysis is highly versatile, underpinning many biological and synthetic transformations.

• Keywords
• biodiesel, esterification, graphene catalysts, heterogeneous acid catalysts, solid acid catalysis, transesterification,
• Publication type
• Journal Article MeSH