Furans represent one of the most important classes of intermediates in the conversion of non-edible lignocellulosic biomass into bio-based chemicals and fuels. At present, bio-furan derivatives are generally obtained from cellulose and hemicellulose fractions of biomass via the acid-catalyzed dehydration of their relative C6-C5 sugars and then converted into a wide range of products. Furfural (FUR) and 5-hydroxymethylfurfural (HMF) are surely the most used furan-based feedstocks since their chemical structure allows the preparation of various high-value-added chemicals. Among several well-established catalytic approaches, hydrogenation and oxygenation processes have been efficiently adopted for upgrading furans; however, harsh reaction conditions are generally required. In this review, we aim to discuss the conversion of biomass derived FUR and HMF through unconventional (transfer hydrogenation, photocatalytic and electrocatalytic) catalytic processes promoted by heterogeneous catalytic systems. The reaction conditions adopted, the chemical nature and the physico-chemical properties of the most employed heterogeneous systems in enhancing the catalytic activity and in driving the selectivity to desired products are presented and compared. At the same time, the latest results in the production of FUR and HMF through novel environmental friendly processes starting from lignocellulose as well as from wastes and by-products obtained in the processing of biomass are also overviewed.

Recent catalytic routes for the preparation and the upgrading of biomass derived furfural and 5-hydroxymethylfurfural

Single atom catalyst, which contains isolated metal atoms singly dispersed on supports, has great potential for achieving high activity and selectivity in hetero-catalysis and electrocatalysis. However, the activity and stability of single atoms and their interaction with support still remains a mystery. Here we show a stable single atomic ruthenium catalyst anchoring on the surface of cobalt iron layered double hydroxides, which possesses a strong electronic coupling between ruthenium and layered double hydroxides. With 0.45 wt.% ruthenium loading, the catalyst exhibits outstanding activity with overpotential 198 mV at the current density of 10 mA cm−2 and a small Tafel slope of 39 mV dec−1 for oxygen evolution reaction. By using operando X-ray absorption spectroscopy, it is disclosed that the isolated single atom ruthenium was kept under the oxidation states of 4+ even at high overpotential due to synergetic electron coupling, which endow exceptional electrocatalytic activity and stability simultaneously. While water splitting offers a carbon-neutral means to store energy, water oxidation is sluggish and corrosive over earth-abundant electrocatalysts. Here, authors show single ruthenium atoms over cobalt-iron layered double hydroxides to be effective and stable oxygen evolution electrocatalysts.

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Boosting oxygen evolution of single-atomic ruthenium through electronic coupling with cobalt-iron layered double hydroxides

Surface Defect Engineering in 2D Nanomaterials for Photocatalysis

Photocatalysis represents a unique class of chemical transformations. It utilizes the energy delivered by light and drives reactions that are difficult, sometimes even impossible, to carry out in dark. When used for thermodynamically uphill reactions such as photosynthesis, photocatalysis promises a sustainable solution to large scale solar energy storage. Despite the longstanding interest in this process and research efforts, existing photocatalysis demonstrations are limited to academic laboratory settings. Chief among the reasons for the slow progress is the lack of suitable photocatalyst materials for large scale applications. For the purpose of effective light absorption, charge separation, and charge transfer, a large number of photocatalytic materials, including conventional semiconductors and emerging photoelectronic materials such as nanoscale plasmonic metal particles, quantum dots, and 2D materials, have been studied. This Review is written to summarize these recent efforts from a broad materia...

Photocatalysis: From Fundamental Principles to Materials and Applications

Photocatalytic degradation of antibiotics using a novel Ag/Ag2S/Bi2MoO6 plasmonic p-n heterojunction photocatalyst: Mineralization activity, degradation pathways and boosted charge separation mechanism

Hierarchical Bi2MoO6 spheres in situ assembled by monolayer nanosheets were successfully prepared via a cetyltrimethylammonium bromide (CTAB)-assisted assembled strategy under different prepared conditions. The structure, morphology and surface chemical state of the prepared samples were well characterized. The AFM images (Atomic force microscopy) present that the average thickness of the nanosheets for two typical samples are about 0.81 and 0.84 nm, respectively. The analysis results of O 1s XPS and in-situ ESR indicate that there are different concentration oxygen vacancies (OVs) in two prepared samples (denoted as Vo-rich and Vo-poor). Time-resolved fluorescence emission decay spectra show that the carriers lifetime of Vo-rich and Vo-poor are 5.18 and 1.59 ns, respectively. Moreover, in-situ FTIR of benzyl alcohol (BA) absorption results suggest that rich oxygen vacancies could facilitate BA coordination. Vo-rich and Vo-poor present 38.2% and 7.1% of conversion with high selectivity for benzyl alcohol oxidation under visible light irradiation, respectively. The higher performance for Vo-rich was attributed to rich oxygen vacancies which act as the sites for the reactant activation. Finally, a feasible reaction mechanism was proposed to elucidate that enhanced photocatalytic activity over the Vo-rich.

Hierarchical Bi2MoO6 spheres in situ assembled by monolayer nanosheets toward photocatalytic selective oxidation of benzyl alcohol

Development and photocatalytic mechanism of monolayer Bi2MoO6 nanosheets for the selective oxidation of benzylic alcohols

The cooperation effect in the Au–Pd/LDH for promoting photocatalytic selective oxidation of benzyl alcohol

A catalyst composed of monolayer nonstoichiometric titanate nanosheets (denoted as TN) and Pd clusters is constructed for precise synthesis of cyclohexanone from phenol hydrogenation with high conversion (>99%) and selectivity (>99%) in aqueous media under light irradiation. Experimental and DFT calculation results reveal that the surface exposed acid and basic sites on TN could interact with phenol molecules in a nonplanar fashion via a hexahydroxy hydrogen-bonding ring to form a surface coordination species. This greatly facilitates the adsorption and activation of phenol molecules and suppresses the further hydrogenation of cyclohexanone. Moreover, the surface Pd clusters serve as the active sites for the adsorption and dissociation of hydrogen molecules to provide active H atoms. The synergistic effect of the surface coordination species, TN and Pd clusters remarkably facilitate the high yield of cyclohexanone in photocatalysis. Finally, the possible thermo/photocatalytic mechanisms on Pd/TN are propo...

Yujie Song

Papers

Hierarchical Bi2MoO6 spheres in situ assembled by monolayer nanosheets toward photocatalytic selective oxidation of benzyl alcohol

Development and photocatalytic mechanism of monolayer Bi2MoO6 nanosheets for the selective oxidation of benzylic alcohols

The cooperation effect in the Au–Pd/LDH for promoting photocatalytic selective oxidation of benzyl alcohol

A Pd/Monolayer Titanate Nanosheet with Surface Synergetic Effects for Precise Synthesis of Cyclohexanones

Photocatalytic synthesis of N-benzyleneamine from benzylamine on ultrathin BiOCl nanosheets under visible light