Noncrystalline Zeolitic Imidazolate Frameworks Tethered with Ionic Liquids as Catalysts for CO2 Conversion into Cyclic Carbonates.

Noncrystalline zeolitic imidazolate frameworks (ZIFs) tethered with ionic liquids (ILs) were successfully employed as catalysts for mild CO2 conversion into cyclic carbonates for the first time. Notably, noncrystalline ZIFs exhibit outstanding catalytic performance in terms of activity, stability, and substrate suitability. Z3 was obtained through the simultaneous incorporation of a boronic acid group and ILs into its ZIF framework and exhibited a superior catalytic activity. A reaction mechanism for the propylene oxide-CO2 cycloaddition has been proposed, which integrates experimental findings with density functional theory calculations. The results indicate that zinc, ILs, and boronic acid play crucial roles in achieving high activity. Zinc and ILs are identified as key contributors to epoxide activation and ring opening, while boronic acid plays a crucial role in stabilizing the turnover frequency-determining transition states. The simplicity of this ZIF synthesis approach, combined with the high activity, stability, and versatility of the products, facilitates practical and efficient conversion of CO2 and epoxides into cyclic carbonates.

Self-Promoted Hydroxyl Radical Releasing Magnetic Zn@Fe Particles.

Semiconductor photocatalysts, such as TiO2 and ZnO, have garnered significant attention for their ability to generate hydroxyl radicals, offering various practical applications. However, the reliance on UV light to facilitate electron-hole separation for hydroxyl radical production poses limitations. In this study, a novel approach is presented utilizing Zn@Fe core/shell particles capable of generating hydroxyl radicals without external energy input. The generation process involves electron donation from Zn to O2 , resulting in the formation of radical species . O2 - /H2 O2 , followed by Fe-catalyzed conversion of H2 O2 into hydroxyl radicals through the Fenton reaction. The release of . OH imparts good antimicrobial and antiviral properties to the Zn@Fe particles. Furthermore, the inclusion of Fe confers magnetic properties to the material. This dual functionality holds promise for diverse potential applications for the Zn@Fe particles.

Metal Catalyst-Free Oxidative C-C Bond Cleavage of a Lignin Model Compound by H2 O2 in Formic acid.

Selective cleavage of the ß-O-4 ether bond of lignin to produce aromatics is one of the most important topics for the sustainable production of chemicals from biomass. A simple system has been developed for Cα -Cß bond cleavage of a ß-O-4 ketone-structured lignin model compound (LMC) by H2 O2 in formic acid under metal catalyst-free conditions. By using this simple system, with H2 O2 , formic acid, and mineral acid catalyst, over 90 % product yield is achieved in 6 h at room temperature. The reaction proceeds through the classic Baeyer-Villiger oxidation and in situ-generated performic acid serves as the key oxidant. The cleavage of alcoholic LMCs by using the presented method in a two-step process is also demonstrated.

ZnO Nanopillar Coated Surfaces with Substrate-Dependent Superbactericidal Property.

ZnO nanopillars coated on various surfaces are able to kill adhered bacteria and fungi due to their physical structure through a rupturing mechanism. Remarkably, zinc foil and galvanized steel surfaces with ZnO nanopillar coatings demonstrate an excellent remote bacteria-killing property. Their bacterial killing efficacy is several orders higher than ZnO nanopillars coated on other surfaces as well as ZnO nanoparticles themselves. Mechanistic study shows that the nanostructure surface kills adhered microbial cells by rupturing the cell wall, while superoxide (• O2- ) released from the ZnO coating with electrons donated from zinc via the Zn/ZnO interface rather than photoirritation is responsible for the superior remote killing. The results of this study represent a novel mechanism of surface disinfection and its application in water disinfection is also demonstrated.

Highly Efficient Gas-Phase Oxidation of Renewable Furfural to Maleic Anhydride over Plate Vanadium Phosphorus Oxide Catalyst.

Maleic anhydride (MAnh) and its acids are critical intermediates in chemical industry. The synthesis of maleic anhydride from renewable furfural is one of the most sought after processes in the field of sustainable chemistry. In this study, a plate vanadium phosphorus oxide (VPO) catalyst synthesized by a hydrothermal method with glucose as a green reducing agent catalyzes furfural oxidation to MAnh in the gas phase. The plate catalyst-denoted as VPOHT -has a preferentially exposed (200) crystal plane and exhibited dramatically enhanced activity, selectivity and stability as compared to conventional VPO catalysts and other state-of-the-art catalytic systems. At 360 °C reaction temperature with air as an oxidant, about 90 % yield of MAnh was obtained at 10 vol % of furfural in the feed, a furfural concentration value that is much higher than those (<2 vol %) reported for other catalytic systems. The catalyst showed good long-term stability and there was no decrease in activity or selectivity for MAnh during the time-on-stream of 25 h. The high efficiency and catalyst stability indicate the great potential of this system for the synthesis of maleic anhydride from renewable furfural.

Highly Selective Deoxydehydration of Tartaric Acid over Supported and Unsupported Rhenium Catalysts with Modified Acidities.

The deoxydehydration (DODH) of sugar acids to industrially important carboxylic acids is a very attractive topic. Oxorhenium complexes are the most-often employed DODH catalysts. Because of the acidity of the rhenium catalysts, the DODH products of sugar acids were usually in the form of mixture of free carboxylic acids and esters. Herein, we demonstrate strategies for the selective DODH of sugar acids to free carboxylic acids by tuning the Lewis acidity or the Brønsted acidity of the rhenium-based catalysts. Starting from tartaric acid, up to 97 % yield of free maleic acid was achieved. Based on our strategies, functional polymer immobilized heterogeneous rhenium catalysts were also developed for the selective DODH conversion of sugar acids.

A highly efficient thiazolylidene catalyzed acetoin formation: reaction, tolerance and catalyst recycling.

An efficient formation of acetoin from acetaldehyde was achieved under thiazolylidene catalysis. High yields and TON were achieved. Its sufficient tolerance toward ethanol and moisture renders it a practical key step of the ethanol upgrading process. A new type of solid supported thiazolylidene catalyst was designed to make catalyst recycling achievable.

Vitamin B1-catalyzed acetoin formation from acetaldehyde: a key step for upgrading bioethanol to bulk C4 chemicals.

The production of bulk chemicals and fuels from renewable biobased feedstocks is of significant importance for the sustainability of human society. The production of ethanol from biomass has dramatically increased and bioethanol also holds considerable potential as a versatile building block for the chemical industry. Herein, we report a highly selective process for the conversion of ethanol to C4 bulk chemicals, such as 2,3-butanediol and butene, via a vitamin B1 (thiamine)-derived N-heterocyclic carbene (NHC)-catalyzed acetoin condensation as the key step to assemble two C2 acetaldehydes into a C4 product. The environmentally benign and cheap natural catalyst vitamin B1 demonstrates high selectivity (99%), high efficiency (97% yield), and high tolerance toward ethanol and water impurities in the acetoin reaction. The results enable a novel and efficient process for ethanol upgrading.

Purification of biomass-derived 5-hydroxymethylfurfural and its catalytic conversion to 2,5-furandicarboxylic Acid.

A simple and effective water extraction method is presented for the purification 5-hydroxylmethylfurfural (HMF) obtained from a biomass dehydration system. Up to 99% of the HMF can be recovered and the HMF in aqueous solution is directly converted to 2,5-furandicarboxylic acid (FDCA) as the sole product. This purification technique allows an integrated process to produce FDCA from fructose via HMF prepared in an isopropanol monophasic system, with an overall FDCA yield of 83% obtained. From Jerusalem raw artichoke biomass to FDCA via HMF prepared in a water/MIBK (methyl isobutyl ketone) biphasic system, an overall FDCA yield of 55% is obtained.

Highly efficient chemical process to convert mucic acid into adipic acid and DFT studies of the mechanism of the rhenium-catalyzed deoxydehydration.

The production of bulk chemicals and fuels from renewable bio-based feedstocks is of significant importance for the sustainability of human society. Adipic acid, as one of the most-demanded drop-in chemicals from a bioresource, is used primarily for the large-volume production of nylon-6,6 polyamide. It is highly desirable to develop sustainable and environmentally friendly processes for the production of adipic acid from renewable feedstocks. However, currently there is no suitable bio-adipic acid synthesis process. Demonstrated herein is the highly efficient synthetic protocol for the conversion of mucic acid into adipic acid through the oxorhenium-complex-catalyzed deoxydehydration (DODH) reaction and subsequent Pt/C-catalyzed transfer hydrogenation. Quantitative yields (99 %) were achieved for the conversion of mucic acid into muconic acid and adipic acid either in separate sequences or in a one-step process.

Ion-exchangeable titanate nanotubes with visible light responsive photocatalytic activities for dyes degradation.

Sn(2+)- and Pb(2+)-substituted NaHTi3O7 nanotubes were prepared by a hydrothermal synthesis method followed by ion-exchange reaction. The samples were characterized by XRD, SEM, TEM, XPS and UV-visible diffuse reflectance spectroscopy. The photocatalytic activities were investigated for the photodegradation of methylene orange (MO) and methylene blue (MB) under visible light irradiation. The results indicate that Sn2+ and Pb2+ substitutions could have significant impacts on the optical properties and photocatalytic activities of samples. Both Sn(2+)- and Pb(2+)-substituted NaHTi3O7 nanotubes show activities for methylene orange and methylene blue photodegradation under visible light irradiation. With better absorption of visible light, the Sn-NaHTi3O7 sample showed higher activity than Pb-NaHTi3O7.

The effects of NaNbO3 particle size on the photocatalytic activity for 2-propanol photodegradation.

The effects of NaNbO3 particle size on the photocatalytic activity were investigated by taking gaseous 2-propanol photodegradation as a model reaction. By varying the loading amount of precursors onto mesoporous SBA-15, nanocrystalline NaNbO3 samples with particle sizes ranging from 3 to 50 nm were successfully synthesized. The particle size and surface area value of templated NaNbO3 change systematically with the change in loading amount of the precursors. The physicochemical characteristics of the samples were examined by techniques such as XRD, SEM, TEM, Raman spectroscopy, and UV-visible diffuse reflectance spectroscopy. The optimum NaNbO3 particle size for the highest photocatalytic activity was found to be 30 nm. The current study also revealed that the NaNbO3 photocatalyst is structure sensitive for 2-propanol photodegradation. The density of active sites on the sample surface decreases as the particle size decreases. Competing effects of factors such as the surface area, changes in electronic structure, defect density, and concentration of reaction active sites determine the optimum particle size of NaNbO3.

Efficient photocatalytic degradation of rhodamine B over CdS sensitized SiO2-HNb3O8 under visible light.

CdS/SiO2-HNb3O8 and CdS-HNb3O8 composite photocatalysts were developed for rhodamine B photodegradation under visible light. The characteristics of samples were investigated by XRD, SEM, TEM, PL, and UV-visible absorption spectroscopy. A liquid phase deposition method and an impregnation-gas phase deposition method were adopted for the loading of CdS onto SiO2-HNb3O8. All the composite materials show improved photocatalytic activities than the component materials for rhodamine B photodegradation under visible light. With better CdS dispersion and expanded interlayer distance of HNb3O8, the CdS/SiO2-HNb3O8 sample prepared by the novel impregnation-gas phase deposition method showed better activity than the counterpart prepared by conventional liquid phase deposition, CdS-pillared HNb3O8, and some reference samples such as P25, nitrogen-doped TiO2, and Bi2WO6. The enhanced photocatalytic activity of the CdS/SiO2-HNb3O8 composite is ascribed to the interface charge transfer between the two component materials, as well as the layered structure and the intercalation properties of SiO2-HNb3O8.

A comparison study of rhodamine B photodegradation over nitrogen-doped lamellar niobic acid and titanic acid under visible-light irradiation.

A solid-state reaction method with urea as a nitrogen precursor was used to prepare nitrogen-doped lamellar niobic and titanic solid acids (i.e., HNb(3)O(8) and H(2)Ti(4)O(9)) with different acidities for visible-light photocatalysis. The photocatalytic activities of the nitrogen-doped solid acids were evaluated for rhodamine B (RhB) degradation and the results were compared with those obtained over the corresponding nitrogen-doped potassium salts. Techniques such as XRD, BET, SEM, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy were adopted to explore the nature of the materials as well as the characteristics of the doped nitrogen species. It was found that the intercalation of the urea precursor helped to stabilize the layered structures of both lamellar solid acids and enabled easier nitrogen doping. The effects of urea intercalation were more significant for the more acidic HNb(3)O(8) sample than for the less acidic H(2)Ti(4)O(9). Compared with the nitrogen-doped KNb(3)O(8) and K(2)Ti(4)O(9) samples, the nitrogen-doped HNb(3)O(8) and H(2)Ti(4)O(9) solid acids absorb more visible light and exhibit a superior activity for RhB photodegradation under visible-light irradiation. The nitrogen-doped HNb(3)O(8) sample performed the best among all the samples. The results of the current study suggest that the protonic acidity of the lamellar solid-acid sample is a key factor that influences nitrogen doping and the resultant visible-light photocatalysis.