Transition-metal-catalyzed transfer hydrogenation with an in situ hydrogen donor has received a great deal of attention from both academia and industry as an alternative to the traditional high-pressure-hydrogen process, owing to its better efficiency, atom economy, and sustainability features. Hydrogen stored in the chemical bonds of formic acid (FA), a promising hydrogen storage compound that could be derived from biomass or reduction of CO2, can be extracted selectively and used for diverse catalytic transformations. This Review summarizes and compares recent progress in catalytic transfer hydrogenation (CTH) via heterogeneous hydrogen transfer from FA. Transformations of biomass-derived platform chemicals (e.g., aromatic units, C5 and C6 sugars, furans, glycerol, fatty acids, levulinic acid (LA)), nitrogen-containing compounds (e.g., nitroarenes, quinolines), and organochlorinated compounds via transfer hydrogenation, hydrogenolysis, and hydrodechlorination (HDC) are outlined. Synthesis strategies of the heterogeneous metal catalysts (e.g., metal and support type, metal–support interaction, single-atom, alloy effect, and confinement effect) and optimization of the reaction conditions (e.g., temperature, solvents, additives, and FA dosages) for enhancing the catalytic activity and regulating the product distribution are presented. Structure–activity relationships based on both dehydrogenation and hydrogenation of metal catalysts as well as the mechanistic interpretation of CTH with FA are also highlighted. Finally, current challenges and outlook for the future development of the field are discussed.

So far, the development of highly active and stable carbon-based electrocatalysts for oxygen reduction reaction (ORR) to replace commercial Pt/C catalyst is a hot topic. In this study, a new nanoporous nitrogen-doped carbon material was facilely designed by two-step pyrolysis of the renewable Lemna minor enriched in crude protein under a nitrogen atmosphere. Electrochemical measurements show that the onset potential for ORR on this carbon material is around 0.93 V (versus reversible hydrogen electrode), slightly lower than that on the Pt/C catalyst, but its cycling stability is higher compared to the Pt/C catalyst in an alkaline medium. Besides, the ORR at this catalyst approaches to a four-electron transfer pathway. The obtained ORR performance can be basically attributed to the formation of high contents of pyridinic and graphitic nitrogen atoms inside this catalyst. Thus, this work opens up the path in the ORR catalysis for the design of nitrogen-doped carbon materials utilizing aquatic plants as starting precursors.

No abstract

No abstract

Catalytic dehydrogenation enables reversible hydrogen storage in liquid organics as a critical technology to achieve carbon neutrality. However, oxidant or base-free catalytic dehydrogenation at mild temperatures remains a challenge. Here, we demonstrate a metal-free carbocatalyst, nitrogen-assembly carbons (NCs), for acceptorless dehydrogenation of N-heterocycles even at ambient temperature, showing greater activity than transition metal–based catalysts. Mechanistic studies indicate that the observed catalytic activity of NCs is because of the unique closely placed graphitic nitrogens (CGNs), formed by the assembly of precursors during the carbonization process. The CGN site catalyzes the activation of C─H bonds in N-heterocycles to form labile C─H bonds on catalyst surface. The subsequent facile recombination of this surface hydrogen to desorb H 2 allows the NCs to work without any H-acceptor. With reverse transfer hydrogenation of various N-heterocycles demonstrated in this work, these NC catalysts, without precious metals, exhibit great potential for completing the cycle of hydrogen storage.

Cost‐effective and environmentally friendly conversion of nitroarenes into value‐added products is desirable but still challenging. In this work, highly dispersed Ni nanoparticles (NPs) supported on N‐doped mesoporous carbon (Ni/NC‐x) were synthesized via novel ion exchange‐pyrolysis strategy. Their catalytic performance was investigated for one‐pot transfer hydroalkylation of nitrobenzene (NB) with EtOH in absence of H2. Interestingly, the catalytic performance could be easily manipulated by tuning the morphology and electronic state of Ni NPs via varying the pyrolysis temperature. It was found that the Ni/NC‐650 achieved 100 % nitrobenzene conversion and approx. 90 % selectivity of N,N‐diethyl aniline at 240 °C for 5 h, more active than those of homogeneous catalysts or supported Ni catalysts prepared by impregnation (Ni/NC‐650‐IM, Ni/SiO2). This can be ascribed to the higher dispersion and better reducibility as well as richer surface basicity of the catalyst. More interestingly, the Ni/NC‐650 catalyst achieved complete conversion of various nitroarenes, yielding imines, secondary amines, or tertiary amines selectively by simply controlling the reaction temperature at 180, 200 and 240 °C, respectively. The one‐pot hydrogen‐free process with non‐noble metal catalysts, as demonstrated in this work, shows great promise for selective conversion of nitroarenes with ethanol to various anilines at industrial scale, from an economic, environmental, and safety viewpoint.

The effect of polyphenol removal (“dephenol”) combined with an alkaline pH shift treatment on the O/W interfacial and emulsifying properties of canola seed protein isolate (CPI) was investigated. Canola seed flour was subjected to solvent extraction to remove phenolic compounds, from which prepared CPI was exposed to a pH12 shift to modify the protein structure. Dephenoled CPI had a light color when compared with an intense dark color for the control CPI. Up to 53% of phenolics were removed from the CPI after the extraction with 70% ethanol. Dephenoled CPI showed a partially unfolded structure and increased surface hydrophobicity and solubility. The particle size increased slightly, indicating that soluble protein aggregates formed after the phenol removal. The pH12 shift induced further unfolding and decreased protein particle size. Dephenoled CPI had a reduced β subunit content but an enrichment of disulfide-linked oligopeptides. Dephenol improved the interfacial rheology and emulsifying properties of CPI. Although phenol removal did not promote peptic digestion and lipolysis, it facilitated tryptic disruption of the emulsion particles due to enhanced proteolysis. In summary, dephenol accentuated the effect of the pH shift to improve the overall emulsifying properties of CPI and emulsion in in vitro digestion.

Selective hydrogenation of biomass-derived phenols into cyclohexanones or cyclohexanols is an industrially important fundamental reaction. Traditional process used commonly noble metal catalysts and high-pressured H2 as donor, which are not...