Recent Progress on Electrocatalytic Valorization of Biomass-Derived Organics

Electrocatalytic valorization of biomass derivatives can be powered by electricity generated from renewable sources such as solar and wind energy.A shift from centralized,high-temperature,and energy-intensive processes to decentralized,low-temperature conversions is achieved,which meets the requirement of sustainable energy generation.This approach provides an efficient,green,and additive-free strategy for biomass derivative valorization,in which product selectivity could be easily regulated by the applied potential and electrocatalyst utilized.However,a scale-up application is still far from being completed due to the inability of conversion rates and selectivity to meet the industrialization requirements.A better understanding of the reaction mechanism and the development of highefficiency and high-selectivity electrocatalysts are required to pave the path toward larger industrialization applications.Herein,we summarize the recent research progress in the electrocatalytic oxidation and hydrogenation of platform compounds such as furanic compounds and glycerol.In the literature,these three research areas are integrated to realize the scale-up application of the processes as mentioned above.The investigations of the mechanism are based on in situ techniques,theoretical calculations,and advanced electrocatalyst studies.Finally,the challenges and prospects in this topic are described.We expect that this review will provide the fundamental understanding and design guidelines to achieve efficient and high-selectivity catalysts and further facilitate the scale-up application of the electrocatalytic conversion of biomass derivatives.

Reductive Conversion of Biomass-Derived Furancarboxylic Acids with Retention of Carboxylic Acid Moiety

Catalytic reduction systems of 2-furancarboxylic acid(FCA)and 2,5-furandicarboxylic acid(FDCA)with H 2 without reduction of the carboxyl groups are reviewed.FCA and FDCA are produced from furfural and 5-hydroxymethylfurfural which are important platform chemicals in biomass conversions.Furan ring hydrogenation to tetrahydrofuran-2-carboxylic acid(THFCA)and tetrahydrofuran-2,5-dicarboxylic acid(THFDCA)easily proceeds over Pd catalysts.Hydrogenolysis of one C–O bond in the furan ring produces 5-hydroxyvaleric acid(5-HVA)and 2-hydroxyadipic acid.2-Hydroxyvaleric acid is not produced in the reported systems.5-HVA can be produced as the lactone form(δ-valerolactone;DVL)or as the esters depending on the solvent.These reactions proceed over Pt catalysts with good yields(~70%)at optimized conditions.Hydrogenolysis of two C–O bonds in the furan ring produces valeric acid and adipic acid,the latter of which is a very important chemical in industry and its production from biomass is of high importance.Adipic acid from FDCA can be produced directly over Pt-MoO_(x) catalyst,indirectly via hydrogenation and hydrodeoxygenation as one-pot reaction using the combination of Pt and acid catalysts such as Pt/niobium oxide,or indirectly via two-step reaction composed of hydrogenation catalyzed by Pd and hydrodeoxygenation catalyzed by iodide ion in acidic conditions.Only the two-step method can give good yield of adipic acid at present.

Cobalt nitride enabled benzimidazoles production from furyl/aryl bio-alcohols and o-nitroanilines without an external H-source

Benzimidazole derivatives have wide-spectrum biological activities and pharmacological effects,but remain challenging to be produced from biomass feedstocks.Here,we report a green hydrogen transfer strategy for the efficient one-pot production of benzimidazoles from a wide range of bio-alcohols and o-nitroanilines enabled by cobalt nitride species on hierarchically porous and recyclable nitrogen-doped carbon catalysts(Co/CN_(x)-T,T denotes the pyrolysis temperature)without using an external hydrogen source and base additive.Among the tested catalysts,Co/CN_(x)-700 exhibited superior catalytic performance,furnishing 2-substituted benzimidazoles in 65%–92%yields.Detailed mechanistic studies manifest that the coordination between Co^(2+)and N with appropriate electronic state on the porous nitrogen-doped carbon having structural defects,as well as the remarkable synergetic effect of Co/N dual sites contribute to the pronounced activity of Co/CN_(x)-700,while too high pyrolysis temperature may cause the breakage of the catalyst Co-N bond to lower down its activity.Also,it is revealed that the initial dehydrogenation of bio-alcohol and the subsequent cyclodehydrogenation are closely correlated with the hydrogenation of nitro groups.The catalytic hydrogen transfer-coupling protocol opens a new avenue for the synthesis of N-heterocyclic compounds from biomass.