Creating and Stabilizing an Oxidized Pd Surface under Reductive Conditions for Photocatalytic Hydrogenation of Aromatic Carbonyls

Ultrahigh-Selectivity Photocatalytic Upgrading of Bio-Aldehydes/Diols to Monoalcohols Via In Situ Circumventing Coupling Co-Products Over Janus Single-Atom Pd/TiO2

Photocatalytic transfer hydrogenation of biomass-derived aldehydes to alcohols often results in unwanted coupling co-products. Herein, an ultraselective hydrogen transfer system enabled by in situ oxidative C─C bond cleavage over a Janus single-atom palladium on titanium dioxide (0.5Pd/TiO2) photocatalyst is presented. The TiO2 carrier promotes hydrogen-donor activation, while Pd single atoms function as both electron and hydrogen transfer centers, enabling photocatalytic conversion of bio-based furfural to furfuryl alcohol in >99% yield using ethanol as solvent/H-donor at 25 °C. The control/in situ experiments and calculations reveal that ethanol on 0.5Pd/TiO2 preferentially activates a co-formed coupling by-product to undergo C─C bond cleavage followed by proton-coupled electron transfer, exclusively producing furfuryl alcohol. 0.5Pd/TiO2 with good reusability is applicable to hydrogenative upgrading of various aldehydes/diols into corresponding monoalcohols with 81‒99% yields. This in situ Janus photocatalytic conversion strategy offers a new approach to eliminate side reactions in reductive upgrading of unsaturated organics/biomass with high selectivity.

Diastereoselective dearomatization of indoles via photocatalytic hydroboration on hydramine-functionalized carbon nitride

A protocol for trans-hydroboration of indole derivatives using heterogeneous photocatalysis with NHC-borane has been developed, addressing a persistent challenge in organic synthesis. The protocol, leveraging high crystalline vacancy-engineered polymeric carbon nitride as a catalyst, enables diastereoselective synthesis, expanding substrate scope and complementing existing methods. The approach emphasizes eco-friendliness, cost-effectiveness, and scalability, making it suitable for industrial applications, particularly in renewable energy contexts. The catalyst's superior performance, attributed to its rich carbon-vacancies and well-ordered structure, surpasses more expensive homogeneous alternatives, enhancing viability for large-scale use. This innovation holds promise for synthesizing bioactive compounds and materials relevant to medicinal chemistry and beyond.

Recent progress of heterogeneous catalysts for transfer hydrogenation under the background of carbon neutrality

Under the background of carbon neutrality, the direct conversion of greenhouse CO2 to high value added fuels and chemicals is becoming an important and promising technology. Among them, the generation of liquid C1 products (formic acid and methanol) has made great progress; nevertheless, it encounters the problem of how to use it efficiently to solve the overcapacity issue. In this review, we suggest that the catalytic transfer hydrogenation using formic acid and methanol as the hydrogen sources is a critical and potential route for the substitution for the fossil fuel-derived H2 to generate essential bulk and fine chemicals. We mainly focus on summarizing the recent progress of heterogeneous catalysts in such reactions, including thermal- and photo-catalytic processes. Finally, we also propose some challenges and opportunities for this development.