Photocatalytic Production of Ethanolamines and Ethylenediamines from Bio-Polyols over a Cu/TiO2 Catalyst.

Valorization of biomass-derived polyols into high-value-added ethanolamines and ethylenediamines is highly attractive. Herein, we report a one-step photocatalytic protocol to convert bio-polyols into a 60 % yield of ethanolamines and ethylenediamines over a multifunctional Cu/TiO2 catalyst. This catalyst enables a tandem process of photocatalytic polyol C-C bond cleavage and reductive amination in one pot at room temperature, and also allows the selective conversion of various bio-polyols and amines. Mechanistic studies revealed that photogenerated holes in TiO2 promote the retro-aldol C-C bond cleavage or oxidative dehydrogenation of polyols, and photogenerated electrons accumulate on small-sized Cu clusters, which facilitate the reductive amination via hydrogen transfer and prevent the H2 generation. This strategy provides new opportunities for the development of non-noble metal photocatalysts and methods of biomass conversion under mild conditions.

Selective Oxidation of Glycerol into Formic Acid by Photogenerated Holes and Superoxide Radicals.

Photocatalysis is a promising technology for conversion of the glycerol into formic acid, but photocatalytic oxidation of C-C bonds in glycerol exhibits poor selectivity towards formic acid because the photogenerated radicals (e.g., hydroxyl radicals) further oxidize formic acid to CO2 . In this work, a synergy of photogenerated holes and superoxide radicals that achieved the selective oxidation of glycerol into formic acid over the TiO2 catalyst was revealed. The charge separation of pristine TiO2 was improved with the aid of oxygen, which resulted in efficient hole oxidation of the C-C bonds in glycerol to formic acid. Surface active species were controlled to prevent being converted to hydroxyl radicals on TiO2 by controlling the oxygen and water contents, which solved the problem of formic acid peroxidation without sophisticated catalyst modifications. Mechanism studies suggested that glyceraldehyde and glycolaldehyde were the intermediates to generate formic acid. This work provides a green and efficient approach to produce formic acid as a liquid hydrogen carrier from bio-based alcohols.

Polar hydrogen species mediated nitroarenes selective reduction to anilines over an [FeMo]Sx catalyst.

We herein present an efficient approach for the chemoselective synthesis of arylamines from nitroarenes and hydrazine over an iron-molybdenum sulfide catalyst ([FeMo]Sx). The heterogeneous hydrogen transfer reduction can be efficiently carried out at 30 °C and provides anilines with 95-99% selectivities. The in situ gas product analysis demonstrates that [FeMo]Sx can catalyze the decomposition of N2H4 to H* species, not H2. Combining with the kinetic analysis of the aniline generation rates from nitrobenzene and intermediates, the nitro group reduction to the nitroso group is confirmed to be the rate-determining step. The positive slope of Hammett's equation suggests that the critical intermediate in the rate-determining step is in the negative state, which suggests that the active H* should be in polar states (Hδ- and Hδ+). These findings will provide a novel route for the synthesis of substituted anilines and broaden the application of MoSx catalysts under mild conditions.

Insight into the origin of SARS-CoV-2 through structural analysis of receptor recognition: a molecular simulation study.

Bats and pangolins are considered to be potential hosts of the new coronavirus SARS-CoV-2, based on its genome similarity to coronaviruses of these species (Bat-CoV-RaTG13 and Pangolin-CoV). The receptor-binding domain (RBD), a functional component of the spike protein, is responsible for binding of SARS-CoV-2 by human ACE2 receptors and is also key to cross-species viral transmission. We performed molecular dynamics (MD) simulations using structures of hACE2 in complex with the RBD of SARS-CoV-2, SARS-CoV, Pangolin-CoV and Bat-CoV-RaTG13, respectively. By analyzing the hydrogen-bonding network at the RBD-hACE2 interface and estimating the binding free energies between RBD and hACE2, we found Pangolin-CoV bound hACE2 in a similar state as did SARS-CoV-2, and both of them bound hACE2 more strongly than did Bat-CoV-RaTG13 or SARS-CoV. We further identified two major adaptation mutations of SARS-CoV-2-RBD, which may have significant roles in regulating the recognition and binding between RBD and hACE2. Our results add to existing evidence that Pangolins have the potential to act as an intermediate host for SARS-CoV-2, and provide guidance for future design of antiviral drugs and vaccines.

Amine-Mediated Bond Cleavage in Oxidized Lignin Models.

Introducing amines/ammonia into lignin cracking will allow novel bond cleavage pathways. Herein, a method of amines/ammonia-mediated bond cleavage in oxidized lignin ß-O-4 models was studied using a copper catalyst at room temperature, demonstrating the effect of the amine source on the selectivity of products. For primary and secondary aliphatic amines, lignin ketone models underwent oxidative Cα -Cß bond cleavage and Cα -N bond formation to generate aromatic amides. For ammonia, the competition between oxygen and ammonia determined the selectivity between Cα -N and Cß -N bond formation, generating amides and α-keto amides, respectively. For tertiary amines, the lignin models underwent oxidative Cα -Cß bond cleavage to benzoic acids. Control experiments indicated that amines act as nucleophiles attacking at the Cα or Cß position of the oxidized ß-O-4 linkage to be cleaved. This study represents a novel example that the breakage of oxidized lignin model can be regulated by amines with a copper catalyst.

Simultaneous measurement of temperature and refractive index based on a hybrid surface plasmon resonance multimode interference fiber sensor.

We propose and demonstrate a hybrid fiber-based sensor combining a multimode interference (MMI) structure and a surface plasmon resonance (SPR) structure for simultaneous measurement of temperature and refractive index (RI) of a liquid sample. We configure the MMI structure by connecting a single-mode fiber, a no-core fiber, and a single-mode fiber sequentially. We set up the SPR structure by coating a gold film with a thickness of 50 nm on the surface of the no-core fiber. We measure the sensitivity of RI and the temperature of the MMI and SPR structure, respectively. Then we obtain the coefficient matrix to simultaneously measure the temperature and RI of a liquid sample and obtain the highest RI sensitivity of 2061.6 nm/RIU and temperature sensitivity of 37.9 pm/°C. We verify the feasibility of the sensor in liquid alcohol. The testing results indicate that the proposed sensor and testing method are feasible, accurate, and convenient.

Photo splitting of bio-polyols and sugars to methanol and syngas.

Methanol is a clean liquid energy carrier of sunshine and a key platform chemical for the synthesis of olefins and aromatics. Herein, we report the conversion of biomass-derived polyols and sugars into methanol and syngas (CO+H2) via UV light irradiation under room temperature, and the bio-syngas can be further used for the synthesis of methanol. The cellulose and even raw wood sawdust could be converted into methanol or syngas after hydrogenolysis or hydrolysis pretreatment. We find Cu dispersed on titanium oxide nanorod (TNR) rich in defects is effective for the selective C-C bond cleavage to methanol. Methanol is obtained from glycerol with a co-production of H2. A syngas with CO selectivity up to 90% in the gas phase is obtained via controlling the energy band structure of Cu/TNR.