No abstract

Chitin is the most abundant biopolymer after cellulose but it has not been fully utilized yet. Because of biologically fixed nitrogen, effective conversion of chitin or its derivatives to value‐added organonitrogen compounds is a promising strategy to valorize chitin biomass, which has attracted increasing attention. Recently, a novel concept of shell biorefinery has been proposed on account of the huge potentials of chitin valorization. Until now, a number of valuable organonitrogen chemicals, including amino sugars, amino alcohols, amino acids, and heterocyclic compounds, have been produced from chitin biomass. In this Minireview, the focus is on the recent advances in the synthesis of organonitrogen chemicals employing chitin biomass as starting material via different catalytic processes. An outlook on the challenges and opportunities for more effective valorization of chitin will be given.

Novel and selective strategies for platform chemical production from renewable biomass are highly attractive in respect to value-added utilization of sustainable resources. In this study, a series of low-cost, commercially available, transition metal carbonates (Zr, Ni, Mg, Zn, and Pb) were investigated for catalytic transfer hydrogenation of levulinate esters to γ-valerolactone (GVL) via the cascade process of Meerwein−Ponndorf−-Verley (MPV) reduction and lactonization reaction. Among the selected catalysts, basic zirconium carbonate is the most active, with the highest turnover frequency (TOF) of 3.1 h −1 and a surface reaction rate of 0.21 mol m −2 h −1 . At 453 K, 3.0 h, and 1.0 MPa N 2 , 100% ethyl levulinate conversion, 96.3% GVL yield, and 91.9% hydrogen donor utilization are observed due to the cooperative effect between acid (M n+ ) and base (−OH) sites. Furthermore, this catalyst shows high recyclability under the optimized conditions, where a satisfactory catalytic activity is shown even after six consecutive runs.

Chitin is one of the most abundant biopolymers on Earth but under-utilized. The effective conversion of chitin biomass to useful chemicals is a promising strategy to make full use of chitin. Among chitin-derived compounds, some furan derivatives, typically 5-hydroxymethylfurfural and 3-acetamido-5-acetylfuran, have shown great potential as platform compounds in future industries. In this review, different catalytic systems for the synthesis of nitrogen-free 5-hydroxymethylfurfural and nitrogen-containing 3-acetamido-5-acetylfuran from chitin or its derivatives are summarized comparatively. Some efficient technologies for enhancing chitin biomass conversion have been introduced. Last but not least, future challenges are discussed to enable the production of valuable compounds from chitin biomass via greener processes.

Summary The CdSe@TiO2 core‐shell nanorod arrays for photoelectrochemical (PEC) application were designed and constructed by a facile electrochemical deposition strategy. The CdSe@TiO2 photoanodes exhibit highly efficient PEC performance under visible light irradiation, among which the CdSe shell layer thickness can be precisely adjusted by different electrodeposition time. In comparison with nude TiO2 nanorods, the optimized CdSe@TiO2 photoanode (TC‐500) shows a significant saturated photocurrent density of 2.1 mA/cm2 at 0 V (vs Ag/AgCl), which is attributed to the good distribution of CdSe nanoparticles on TiO2 nanorod arrays, the favorable band alignment, and the intimate interfacial interaction between CdSe nanoparticles and TiO2 nanorods. The introduction of CdSe shell layer does not only improve light absorption ability but also enhances photogenerated charge carrier's transfer and separation. This current work systematically studies the accurate adjustment of CdSe shell layer thickness on TiO2 nanorod arrays by electrochemical deposition strategy and provides a paradigm to design and fabricate heterostructure composite for PEC application.