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Heteroatom (such as Ti, Sn, Zr, and Hf) zeolites that contain Lewis acid site (LAS) centers with tetrahedral coordination confined in micropores with various topologies are able to catalyze reactions distinct from those catalyzed by Brønsted acid sites (BASs). In particular, these LAS centers are able to coordinate with two oxygen atoms of one or two oxygenated molecules on a single LAS simultaneously, which are suitable for the conversion of biomass-derived oxygenates via unique reaction pathways, and have been widely explored in the conversion of biomass-derived oxygenates to value-added products. In this review, methods of conventional hydrothermal synthesis, improved direct synthesis (such as interzeolite transformation and dry gel conversion) and post-synthesis (such as solid-state ion change, structural reconstruction and grafting) are compared. Next, approaches for the qualification and quantification of the location (framework or extra-framework), fine structure (closed or open), and acidity of heteroatom centers are summarized. Thereafter, we present the applications of Lewis acid zeolites in the conversion of platform oxygenates of hexoses, furan derivatives and acid derivatives via reactions of isomerization, Meerwein–Ponndorf–Verley reduction, oxidation, and ketonization. Notably, the integration of multiple steps into a one-pot cascade reaction for the conversion of oxygenates (for example, glucose to 5-hydroxymethylfurfural and furfural to γ-valerolactone) mediated by the synergy of LASs and BASs or metal sites is also discussed. Finally, the opportunities and challenges in the low-cost synthesis and large-scale application of Lewis acid zeolites for the green and sustainable synthesis of chemicals are proposed. [ABSTRACT FROM AUTHOR]

The selective photocatalytic reduction of CO2 to CH4 remains a challenge because there is a need for not only strong adsorption sites for the intermediates, but also optimal proton-feeding sites on the photocatalyst surface. Herein, a synergistic dual-site function between in situ-generated Ni0 and Ni2P on carbon nitride nanosheets (CN) for photocatalytic reduction of CO2 to CH4 is presented. The highest CH4 production rate of 69.03 μmol g−1 h−1 is achieved on Ni2P/CN-0.5 in an aqueous suspension. Detailed analyses show that the promotion of CH4 is closely correlated with the formation of Ni0 sites due to light irradiation, which is confirmed by tracking the compositions of Ni2P/CN-0.5 through XPS and HRTEM characterization. Density functional theory calculations have been combined with CO-TPD and in situ FTIR spectra to reveal the synergy between in situ-generated Ni0 sites and Ni2P. It shows that the Ni0 sites can stabilize the key intermediate *CO, while the Ni0–Ni2P interface can promote *H transfer from Ni2P to Ni0. Therefore, the CO intermediates are rapidly protonated to form CHO* instead of being desorbed from the surface to produce CO, and subsequently CHO* will be converted into CH4. This work demonstrates a new strategy of designing highly efficient photocatalysts with synergistic catalytic sites for CO2 conversion to hydrocarbons. [ABSTRACT FROM AUTHOR]

Cu 2 O based electrocatalysts generally exhibit better selectivity for C 2 products (ethylene or ethanol) in electrochemical carbon dioxide reduction. The surface characteristic of the mixed Cu + and Cu 0 chemical state is believed to play an essential role that is still unclear. In the present study, density functional theory (DFT) calculations have been performed to understand the role of copper chemical states in selective ethanol formation using a partially reduced Cu 2 O surface model consisting of adjacent Cu + /Cu 0 sites. We mapped out the free energy diagram of the reaction pathway from CO intermediate to ethanol and discussed the relation between the formation of critical reduction intermediates and the configuration of Cu + /Cu 0 sites. The results showed that Cu + sites facilitate the adsorption and stabilization of *CO, as well as its further hydrogenation to *CHO. More importantly, as compared to the high reaction energy (1.23 eV) of the dimerization of two *CO on Cu + /Cu 0 sites, the preferable formation of *CHO on the Cu + site makes the C-C coupling reaction with *CO on the Cu 0 site happen under a relatively lower energy barrier of 0.58 eV. Furthermore, the post C-C coupling steps leading to the formation of the key intermediate *OCHCH 2 to C 2 compound are all thermodynamically favoured. Noteworthily, it is found that *OCHCH 2 inclines to the ethanol formation because the coordinatively unsaturated Cu + site could maintain the C-O bond of *OCHCH 2 , and the weak binding between *O and Cu + /Cu 0 sites helps inhibit the pathway toward ethylene. These findings may provide guidelines for the design of CO and CO 2 reduction active sites with enhanced ethanol selectivity., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Glycerol can be effectively converted to synthesis gas (selectivity higher than 80%) with small amounts of water or no water using plasmas at low temperature and atmospheric pressure, without external heating.