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The selective photocatalytic C–C bond cleavage of biomass coupling with H–O bond cleavage of water for co-producing chemicals and H2 is of great significance, but limited successes have been reported. In this study, a RuS2@CN-x photocatalyst with only exposed crystal face (200) was prepared by anchoring RuS2 nanoparticles on carbon nitride (CN) nanosheets and successfully used in photocatalytic C–C bond cleavage of biomass-based sugars coupling with water splitting to co-generate lactic acid and hydrogen. Interestingly, the RuS2 (200) crystal face combined with the interfacial synergism between CN and RuS2 in RuS2@CN-x effectively improved visible light absorption and enhanced the transfer/separation efficiency of photo-generated carriers. The RuS2@CN-2 exhibited superior photocatalytic activity towards synchronous water splitting and biomass conversion to co-produce hydrogen (8698.3 μmol g−1 h−1) and lactic acid (91.5%). Furthermore, the experimental and DFT calculation results indicated that the exposed crystal face (200) of RuS2 significantly enhanced the photocatalytic activity of RuS2@CN-2. Moreover, this reaction system not only has excellent recyclability but also displays excellent universality for small molecule biomass-derived monosaccharides and macromolecular xylan. This work provides a novel route to efficiently co-produce hydrogen and fine chemicals from photocatalytic C–C bond cleavage of biomass coupling with H–O bond cleavage of water. [ABSTRACT FROM AUTHOR]

Selective oxidation of biomass-based monosaccharides into value-added sugar acids is highly desired, but limited success of producing d-xylonic acid has been achieved. Herein, we report an efficient catalyst system, viz., Au nanoparticles anchored on the inner walls of hollow Al2O3 nanospheres (Au@h-Al2O3), which could catalyze the selective oxidation of d-xylose into d-xylonic acid under base-free conditions. The mesoporous Al2O3 shell as the adsorbent first adsorbed d-xylose. Then, the interface of Au nanoparticles and Al2O3 as active sites spontaneously dissociated O2, and the exposed Au nanoparticle surface as the catalytic site drove the transformation. With this catalyst system, the valuable d-xylonic acid was produced with excellent yields in the aerobic oxidation of d-xylose. Extensive investigation showed that Au@h-Al2O3 is an efficient catalyst with high stability and recyclability. [ABSTRACT FROM AUTHOR]

Residual lignin plays an inhibitory role in the enzymatic hydrolysis of cellulosic biomass. In this study, we examined the structural changes in isolated lignins from the hot water hydrothermal pretreatment of aspen and their inhibitory effects on the enzymatic hydrolysis of Avicel. The functional groups of the isolated lignins were determined using quantitative 13C, 2D HSQC and 31P NMR. The increase in pretreatment severity significantly increased the condensed and non-condensed syringyl and guaiacyl OH group content in the isolated lignins, but decreased the aliphatic OH, p-hydroxybenzoate OH and carboxylic OH group content. A compelling adverse association (r2 = 0.998) was observed between the condensed syringyl and guaiacyl phenolic OH group content in lignins and their inhibitory effects on enzymatic hydrolysis. Langmuir adsorption isotherms showed that a higher pretreatment severity resulted in a higher binding ability between the isolated lignins and the cellulase enzymes, which led to more non-productive binding. It is hypothesized that condensed syringyl and guaiacyl phenolic units are mainly responsible for the inhibitory effect of lignin on enzymatic hydrolysis, in which the condensed aromatic rings enhance the hydrophobic interactions and the phenolic OH group boosts the hydrogen bonding. The combination of hydrophobic interactions and hydrogen bonding can further intensify undesirable non-productive binding. [ABSTRACT FROM AUTHOR]

The selective photocatalytic C–C bond cleavage of biomass coupling with H–O bond cleavage of water for co-producing chemicals and H2 is of great significance, but limited successes have been reported. In this study, a RuS2@CN-x photocatalyst with only exposed crystal face (200) was prepared by anchoring RuS2 nanoparticles on carbon nitride (CN) nanosheets and successfully used in photocatalytic C–C bond cleavage of biomass-based sugars coupling with water splitting to co-generate lactic acid and hydrogen. Interestingly, the RuS2 (200) crystal face combined with the interfacial synergism between CN and RuS2 in RuS2@CN-x effectively improved visible light absorption and enhanced the transfer/separation efficiency of photo-generated carriers. The RuS2@CN-2 exhibited superior photocatalytic activity towards synchronous water splitting and biomass conversion to co-produce hydrogen (8698.3 μmol g−1 h−1) and lactic acid (91.5%). Furthermore, the experimental and DFT calculation results indicated that the exposed crystal face (200) of RuS2 significantly enhanced the photocatalytic activity of RuS2@CN-2. Moreover, this reaction system not only has excellent recyclability but also displays excellent universality for small molecule biomass-derived monosaccharides and macromolecular xylan. This work provides a novel route to efficiently co-produce hydrogen and fine chemicals from photocatalytic C–C bond cleavage of biomass coupling with H–O bond cleavage of water. [ABSTRACT FROM AUTHOR]