A bimetallic nanocatalyst with unique surface configuration displays extraordinary performance for converting biomass-derived polyols to chemicals, with potentially much broader applications in the design of novel catalysts for several reactions of industrial relevance. The synthesis of nanostructured metal catalysts containing a large population of active surface facets is critical to achieve high activity and selectivity in catalytic reactions. Here, we describe a new strategy for synthesizing copper-based nanocatalysts on reduced graphene oxide support in which the catalytically active {111} facet is achieved as the dominant surface by lattice-match engineering. This method yields highly active Cu-graphene catalysts (turnover frequency = 33-114 mol/g atom Cu/h) for converting biopolyols (glycerol, xylitol, and sorbitol) to value-added chemicals, such as lactic acid and other useful co-products consisting of diols and linear alcohols. Palladium incorporation in the Cu-graphene system in trace amounts results in a tandem synergistic system in which the hydrogen generated in situ from polyols is used for sequential hydrogenolysis of the feedstock itself. Furthermore, the Pd addition remarkably enhances the overall stability of the nanocatalysts. The insights gained from this synthetic methodology open new vistas for exploiting graphene-based supports to develop novel and improved metal-based catalysts for a variety of heterogeneous catalytic reactions.

Direct oxidation of glucose with enhanced selectivity to glucaric acid with tartronic and oxalic acids as coproducts is reported using bimetallic PtPd/TiO 2 catalysts under mild conditions. Bimetallic PtPd catalysts display significantly enhanced catalytic activity (turnover frequency (TOF) 2404 h −1 ) and improved selectivity to glucaric acid (S 44%) in glucose oxidation compared to monometallic catalysts (TOF 248 h −1 , S 4%). Oxidation of glucose follows a consecutive reaction with gluconic acid as an intermediate with inhibition of the second step (to glucaric acid and C−C cleavage reactions) by the presence of glucose. Surface characterization using TEM, SEM, chemisorption, UV−vis spectroscopy, and XRD distinguished the particle morphologies and provided insights into structure−activity relations. A reaction pathway for glucose oxidation is proposed based on the product distribution. These results provide new insights into the design of bimetallic catalysts for the oxidation of glucose to glucaric acid.

Aqueous‐phase hydrodeoxygenation (APH) of bioderived feedstocks into useful chemical building blocks is one the most important processes for biomass conversion. However, several technological challenges, such as elevated reaction temperature (220–280 °C), high H2 pressure (4–10 MPa), uncontrollable side reactions, and intensive capital investment, have resulted in a bottleneck for the further development of existing APH processes. Catalytic transfer hydrogenation (CTH) under much milder conditions with non‐fossil‐based H2 has attracted extensive interest as a result of several advantageous features, including high atom efficiency (≈100 %), low energy intensity, and green H2 obtained from renewable sources. Typically, CTH can be categorized as internal H2 transfer (sacrificing small amounts of feedstocks for H2 generation) and external H2 transfer from H2 donors (e.g., alcohols, formic acid). Although the last decade has witnessed a few successful applications of conventional APH technologies, CTH is still relatively new for biomass conversion. Very limited attempts have been made in both academia and industry. Understanding the fundamentals for precise control of catalyst structures is key for tunable dual functionality to combine simultaneous H2 generation and hydrogenation. Therefore, this Review focuses on the rational design of dual‐functionalized catalysts for synchronous H2 generation and hydrogenation of bio‐feedstocks into value‐added chemicals through CTH technologies. Most recent studies, published from 2015 to 2018, on the transformation of selected model compounds, including glycerol, xylitol, sorbitol, levulinic acid, hydroxymethylfurfural, furfural, cresol, phenol, and guaiacol, are critically reviewed herein. The relationship between the nanostructures of heterogeneous catalysts and the catalytic activity and selectivity for C−O, C−H, C−C, and O−H bond cleavage are discussed to provide insights into future designs for the atom‐economical conversion of biomass into fuels and chemicals.

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The human SLC26 transporter family exhibits various transport characteristics, and family member SLC26A9 performs multiple roles, including acting as Cl-/HCO 3 exchangers, Clchannels, and Na + transporters. Some mutations of SLC26A9 are correlated with abnormalities in respiration and digestion systems. As a potential target colocalizing with CFTR in cystic fibrosis patients, SLC26A9 is of great value in drug development. Here, we present a cryo-EM structure of the human SLC26A9 dimer at 2.6 Å resolution. A segment at the C-terminal end is bound to the entry of the intracellular vestibule of the putative transport pathway, which has been proven by electrophysiological experiments to be a gating modulator. Multiple chloride and sodium ions are resolved in the high-resolution structure, identifying novel ion-binding pockets for the first time. Together, our structure takes important steps in elucidating the structural features and regulatory mechanism of SLC26A9, with potential significance in the treatment of cystic fibrosis.

Conversion of renewable biopolyols to valueadded chemicals such as lactic acid and glycols usually demands excess hydrogen/oxygen or harsh reaction conditions in strong alkaline medium (220−350°C). This unfortunately promotes significant side reactions resulting in low carbon selectivity to liquid products, posing significant challenges for the development of sustainable technologies. We report here a new atom economical catalytic conversion of various biopolyols (glycerol, xylitol, mannitol, and sorbitol) to lactic acid with glycols and linear alcohols as co-products at much lower temperatures (115−160°C) without external addition of either hydrogen or oxygen. Among various metal-based catalysts (Pt, Pd, Rh, Ru, Raney Ni, Raney Co, and Cu) evaluated, Pt/C catalyst gives the highest chemoselectivity (S > 95%) for lactic acid, glycols, and linear alcohols at 115−160°C. An important finding is that approximately two-thirds of the hydrogen generated in situ via dehydrogenation of polyols over Pt/C catalyst is efficiently utilized for the conversion of the remaining polyols and intermediates to useful products (e.g., glycols and linear alcohols instead of gaseous products) with the remaining available hydrogen for use elsewhere in a biorefinery. The Pt/C catalyst is thus multifunctional facilitating tandem dehydrogenation/ hydrogenolysis of polyols. Furthermore, it is observed that Ba 2+ alkali ion promotes the activity of the Pt/C catalyst by almost 12-fold compared to other alkali promoters such as NaOH, KOH, and Ca(OH) 2 . In addition to being the first reported study on the conversion of C 5 ∼C 6 polyols (e.g., xylitol and sorbitol) to lactic acid at relatively low temperatures, the results also provide new insights into the mechanism of tandem catalysis of biopolyols conversion to value-added commodity chemicals.

We report for the first time the performance of hybridized Cu/CaO-Al 2 O 3 catalysts for aqueous-phase hydrogenolysis of sorbitol to ethylene glycol (EG), 1,2-propanediol (1,2-PDO), and 1,2-butanediol (1,2-BDO) with linear alcohols as coproducts in a base-free liquid phase. These supported Cu catalysts with solid bases as promoters show significant activity for C−C cleavage and high selectivity (∼84%) to glycols and linear alcohols. The effects of Cu loading, catalyst pretreatment conditions, H 2 pressure, and temperature on activity and selectivity of Cu/CaO-Al 2 O 3 catalysts were investigated. The strong interaction between Cu and Ca 2+ cations in the solid support is found to facilitate C−C and C−O cleavage of sorbitol, as evidenced from TEM, SEM, and TPR studies of the catalysts. Surface characterization and activity tests further suggest that Ca x Cu y Al z O p (Phase I) promotes dehydrogenation and isomerization reactions, whereas spinal CuAl 2 O 4 (Phase II) species facilitates hydrogenation reactions. In addition, the overall activity and selectivity of the Cu catalysts may be easily tuned by the Cu/Ca 2+ molar ratio and catalyst preparation conditions. Cu/CaO-Al 2 O 3 catalysts also give higher overall yields of value-added glycols (63−82%) for facile conversion of various other sugar polyols such as glycerol (C 3 ), erythritol (C 4 ), xylitol (C 5 ), and mannitol (C 6 ) under similar reaction conditions. A surface reaction mechanism involving the formation of β-ketoses on multifunctional Cu−Ca 2+ sites is proposed.