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Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals. Herein, the hydroxyapatite (HAP) supported palladium (Pd) species were fabricated by impregnation and subsequent calcination. The as-obtained heterogeneous Pd catalyst afforded not only excellent selectivity to glyceric acid (GLA) up to 90% with 59% conversion of glycerol but also good recyclability by using molecular oxygen as an oxidant under mild conditions. The characterization of catalysts indicated that both the surface basicity and Pd sites on the catalyst played a crucial role in promoting glycerol oxidation. Notably, it demonstrated that the presence of the vicinal hydroxyl group of glycerol molecule can assist the oxidation reaction via forming a coordination between the vicinal hydroxyl group and Ca2+ sites on HAP-derived catalysts. In this catalytic process, the secondary hydroxyl of glycerol kept untouched and the primary hydroxyl of glycerol was converted into carboxyl group, while the Pd species acted as active centers for cooperatively promoting the subsequent oxidation to generate GLA. Additionally, this catalytic system can be extended widely for the oxidative conversion of other vicinal diols into the corresponding α-hydroxycarboxylic acids selectively. Isotope labeling experiment using H218O confirmed that H2O not only acted as solvent but also was involved in the catalytic cycles. On the basis of the results, a possible reaction mechanism has been proposed. The HAP-supported Pd catalytic system has been shown to serve as an effective approach for the upgrading of bio-derived vicinal diols to high value-added chemicals.

The shortage of resources and the destruction of the environment have caused serious resource and environmental problems shared by all countries around the world. As a ubiquitous renewable resource, biomass has great prospects for replacing fossil energy and attracted attention from the society. The use of catalytic approach to transform biomass into high-value chemicals is an effective way to use biomass efficiently. In this work, Ni-supported catalysts has been developed for the selective cleavage of C–O bonds in lignin model compounds with 2-propanol as the hydrogen source solvent. Among these catalysts, it was indicated that zirconium phosphate (ZrP)-supported Ni catalysts were highly efficient and recyclable for alkyl-aryl ether (α-O-4 and β-O-4) cleavage in lignin model compounds. The further investigation demonstrated that the transfer hydrogenolysis of the C–O bond is highly selective, which afforded phenols and aromatics as dominant products without the products arising from hydrogenation of aromatic rings. Through a series of characterization of the catalyst, it was demonstrated that the medium strong acid sites of the ZrP support promoted the cleavage of alkyl-aryl ethers (α-O-4 and β-O-4), and Bronsted acid sites favored for achieving high selectivity toward C–O bond cleavage. Additionally, Ni(0) sites on the ZrP catalysts were responsible for the catalytic transfer hydrogenolysis.

Co@CoO core–shell nanoparticles featured as metal Co(0) cores wrapped by CoO shells were constructed via a solvent-thermal process in deep eutectic solvents and showed superior activity and stability for the hydroformylation of olefins.

Selective hydrogenolysis of biomass-derived glycerol into 1,2-propanediol (1,2-PDO) is of practical importance to upgrade the huge amounts of surplus glycerol derived from renewable biomass. Herewith, we report that hydrotalcite-derived catalysts have been employed for selective hydrogenolysis of glycerol into 1,2-PDO under aqueous phase and base-free conditions. In particular, the catalyst of Co₂-Ca₄-Al₃ was recorded as a good catalyst with an optimum glycerol conversion of 100% and 1,2-PDO selectivity of 90.5% in glycerol hydrogenolysis. Meanwhile, it exhibited high stability in consecutive catalytic recycles under batch-wise operation conditions. Furthermore, the catalyst also demonstrated high glycerol conversion (ca. 95.0%) and selectivity to 1,2-PDO (ca. 90.0%) with a long-term catalytic stability (280 h) by a continuous-flow fixed-bed reactor. Additionally, the catalyst can be further extended to selective hydrogenolysis of some other sugar polyols to 1,2-PDO (selectivity up to 50.5%–68.5%). The activity tests and characterizations demonstrated that Co⁰ existing in the catalysts acted as active sites in glycerol hydrogenolysis. Also, the further characterization by XRD, HRTEM, and EDS element maps revealed that the distribution of Co was basically consistent with that of Al, while Ca species were adjacent to Co and Al species. The mixed metal oxides CaO-CoAl₂O₄ were generated arising from a strong interaction between Co(II) and Ca(II) oxides species, which endowed more electron-deficient Co(II) sites and also led to large amounts of moderate basic sites, being favorable for enhancing catalytic activity and selectivity. Notably, the forming CaCO₃ phase played a crucial role in preventing the leaching of moderate basic sites and metal species by covering CaO-CoAl₂O₄ mixed metal oxides, which was the crucial reason that the present Co₂-Ca₄-Al₃ catalyst showed the remarkable catalytic stability under aqueous phase reaction conditions. On the basis of the results above, the reaction pathway has been discussed as well.

Novel ionic materials derived from ruthenium cluster cation and tungstoaluminate anions have been developed and are proved to be robust, efficient and recyclable catalysts toward the selective hydrogenation of methyl levulinate (ML) to gamma-valerolactone (GVL) or methyl 4-hydroxypentanoate (4-HPTM) by tuning the acidity. The structure and properties of the catalysts were characterized using elemental analysis, 1H NMR, 27Al NMR, FT-IR, X-ray diffraction, and pyridine absorbed FT-IR, etc. The catalysts not only afforded excellent conversion and selectivity for GVL (99%) or 4-HPTM (88%) in the aqueous phase under very mild conditions (25 °C) but also showed good recyclability in five consecutive cycles without any significant loss in catalytic activity. In contrast to the direct intramolecular esterification of 4-HPTM in most previous reports, further characterization revealed that intramolecular cyclization proceeded via a metal and counterion (tungstoaluminate)-assisted mechanism on the anchored Ru cluster catalyst; moreover, the strong acidity on the catalysts can hamper the conversion of 4-HPTM into GVL. This rendered the Ru cation complex/tungstoaluminate ionic materials a potential candidate for the efficient production of either GVL or 4-HPTM from ML hydrogenation under very mild conditions.

Catalytic hydrogenations represent fundamental processes and allow for atom-efficient and clean functional group transformations for the production of chemical intermediates and fine chemicals in chemical industry. Herein, the Ru/CoO nanocomposites have been constructed and applied as nanocatalysts for the hydrogenation of phenols and furfurals into the corresponding cyclohexanols and tetrahydrofurfuryl alcohols, respectively. The functionalized ionic liquid acted not only as a ligand for stabilizing the Ru/CoO nanocatalyst but also as a thermoregulated agent. The as-obtained nanocatalyst showed superior activity, and it could be conveniently recovered via the thermoregulating phase separation. In six recycle experiments, the catalysts maintained excellent performance. It was observed that the catalytic performance highly hinged on the molar ratio of Ru to Co in the nanocatalyst. The catalyst characterization was carried out by high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectroscopy, X-ray diffraction, high-resolution mass spectrometry, Fourier transform infrared, nuclear magnetic resonance, and UV-vis. Especially, the characterization by HRTEM and HAADF-STEM images of the nanocatalyst demonstrated that Ru(0) and Co(II) species were distributed uniformly and the Ru and Co(II) species were close to each other. However, Co(0) was generated and an electronic transfer from Co to Ru species could occur under the hydrogenation conditions. The 13C NMR characterization indicated further that Co(II) sites were mainly responsible for phenol adsorption. Meanwhile, the adjacent electron-rich Ru(0) sites can promote H2 dissociation and favor for the sequential hydrogenation.

We have developed a Keggin polyoxometalate (POM)-based ionic-liquid (IL)-immobilizing rhodium single-atom Rh catalyst (MTOA)

This work presented the synthesis and characterization of new ionic liquid-coordinating ruthenium complexes. The resulting ruthenium complexes exhibited not only excellent thermoregulated phase-separation behavior but also highly catalytic activity and enantioselectivity for the asymmetric hydrogenation with molecular hydrogen. The thermoregulated ionic liquid catalyst was highly resistant to leaching and was recycled consecutively for six times without significant loss of catalytic activity and enantioselectivity. The presence of Ru H species revealed that NH and a Ru H unit, involved in the hydride transfer process, were of great importance in the present catalytic system.

Polyoxometalate polymers with high proton conductivity are accessed for the first time by controlled covalent polymerization of Wells–Dawson-type niobotungstate and organoboronic acid monomers. The resulting polymer features a purely inorganic backbone, organic sidechains, and acts as a solid-state proton conductor. The controlled bottom‐up design of polymers with metal oxide backbones is a grand challenge in materials design, as it could give unique control over the resulting chemical properties. Herein, we report a 1D‐organo‐functionalized polyoxometalate polymer featuring a purely inorganic backbone. The polymer is self‐assembled from two types of monomers, inorganic Wells–Dawson‐type polyoxometalates, and aromatic organo‐boronates. Their covalent linkage results in 1D polymer strands, which combine an inorganic oxide backbone (based on B−O and Nb−O linkages) with functional organic side‐chains. The polymer shows high bulk proton conductivity of up to 1.59×10−1 S cm−1 at 90 °C and 98 % relative humidity. This synthetic approach could lead to a new class of organic–inorganic polymers where function can be designed by controlled tuning of the monomer units., publishedVersion

Four lanthanide derivatives of Ta-containing POMs [Ln3(H2O)22][P2W15Ta3O62]·nH2O (Ln = La, 1; Ce, 2; Pr, 3; and Nd, 4) were isolated by the self-assembly of Wells–Dawson type Ta/W mixed-addendum POM and lanthanide ions. Compound 1 showed excellent proton conduction performance at high relative humidities (RHs), with conductivity reaching 1.26 × 10−2 S cm−1 at 95 °C under 98% RH.

The heterogeneous heteropolyacid-catalyzed acetalization of glycerol with acetone was investigated under solvent-free conditions. In this work, the calcined Ta/W mixed addenda heteropolyacid catalyst ({H20}-355) was employed as a solid acid catalyst and showed much higher activity than these soluble Keggin-type catalysts in the acetalization of glycerol with acetone due to its superacidity (H0 = −12.95). Meanwhile, it showed high stability in catalytic recycles and extended for acetalization of glycerol with the other aldehydes and ketones. Based on the catalyst characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), 31P NMR spectra, FT-IR spectra, pyridine-absorbed FT-IR, and Hammett acidity functions (H0) by UV–vis spectroscopy, it was found that the acidic strength of the Ta/W mixed addenda heteropolyacid was highly dependent on the contents of crystalline water that could be tuned by calcination temperature. Notably, the solid superacid catalyst {H20}-355 was swollen by acetone, exhibiting an interesting “pseudo-liquid” behavior, which served as a microreactor and facilitated the reaction. Furthermore, after the acetalization reaction of glycerol with furfural (98% yield of acetal) on {H20}-355 catalyst, the furan ring of the acetal products can be hydrogenated sequentially into dioxolane or dioxane with Pd/C catalyst under room temperature condition without the need of any isolation procedure.

A new HPAs H20[P8W60Ta12(H2O)4(OH)8O236]·125H2O (H-1) which comprises a Ta/W mixed addenda heteropolyanion, 20 protons, and 125 crystalline water molecules has been prepared through ion-exchange method. The structure and properties of H-1 have been explored in detail. AC impedance measurements indicate that H-1 is a good solid state proton conducting material at room temperature with a conductivity value of 7.2×10−3 S cm−1 (25 °C, 30% RH). Cyclic voltammograms of H-1 indicate the electrocatalytic activity towards the reduction of nitrite. Hammett acidity constant H0 of H-1 in CH3CN is −2.91, which is the strongest among the present known HPAs. Relatively, H-1 exhibits excellent catalytic activities toward acetal reaction.

Large-scale isolation of nanocrystals of rare-earth-polyoxometalates (RE-POMs) catalysts is important in fundamental research and applications. Here, we synthesized a family of monomeric RE-POMs by the self-assembly of Ta/W mixed-addendum POM {P2W15Ta3O62} and rare-earth (RE) ions. These RE-POMs with molecular formulas of [RE(H2O)7]3P2W15Ta3O62·nH2O (RE = Y, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) are all electroneutral molecular clusters, insoluble in water and common organic solvents. The electronic structures, electrochemical properties, and catalytic activities of them have been investigated by experimental and computational methods. In particular, based on a mild and controllable synthetic process, a convenient and controllable approach to prepare nanocrystals and self-organized aggregates of these monomers has been developed. They exhibit remarkable heterogeneous catalytic activity for cyanosilylation. Both the increased Lewis acid strength of RE in the title compounds, as indicated by theoretical c...

A new HPAs H20[P8W60Ta12(H2O)4(OH)8O236]·125H2O (H-1) which comprises a Ta/W mixed addenda heteropolyanion, 20 protons, and 125 crystalline water molecules has been prepared through ion-exchange method. The structure and properties of H-1 have been explored in detail. AC impedance measurements indicate that H-1 is a good solid state proton conducting material at room temperature with a conductivity value of 7.2×10−3 S cm−1 (25 °C, 30% RH). Cyclic voltammograms of H-1 indicate the electrocatalytic activity towards the reduction of nitrite. Hammett acidity constant H0 of H-1 in CH3CN is −2.91, which is the strongest among the present known HPAs. Relatively, H-1 exhibits excellent catalytic activities toward acetal reaction.

A new sandwich-type polyoxometalate, Na5H[N(CH3)4]2[Co(C3N2H4)2(H2O)4][Co4(H2O)2(PW9O34)2]·21H2O (1), has been synthesized. 1 is composed of a Weakley-type polyanion, [Co4(H2O)2(PW9O34)2]10−, four kinds of cations (five Na+, two [N(CH3)4]+, one [Co(C3N2H4)2(H2O)4]2+ and one H+), and 21 crystalline H2O molecules. The surface oxygen of the polyanion in 1, the crystalline water, and coordinated water molecules make an extended three-dimensional hydrogen bonding network. Alternating current (AC) impedance experiments of 1 reveal good proton conductivity for 1 of 5.03×10−4 S·cm−1 at 25 °C under 98% relative humidity (RH). Activation energy of 1 calculated from Arrhenius plots is 0.358 eV, indicating Grotthuss mechanism is dominant in the proton transfer. Thermal decomposition behavior of 1 was examined by thermogravimetry/mass spectrometry (TG/MS) measurements.