Kangle Lv

Selective aerobic oxidation of the biomass-derived precursor 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid under mild conditions over a magnetic palladium nanocatalyst

A new method for the selective aerobic oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) has been developed employing a magnetically separable [γ-Fe2O3@HAP-Pd(0)] catalyst. The catalyst was prepared by the exchange of Pd2+ with Ca2+ in γ-Fe2O3@HAP, followed by reduction of the Pd2+ to Pd(0) nanoparticles, and well characterized by TEM, XRD and XPS. The catalyst showed high activity in the oxidation of HMF to FDCA in water, with 97% HMF conversion and a 92.9% yield of FDCA under optimal reaction conditions. The method developed has demonstrated some advantages, including its sole requirement of a stoichiometric base, and high catalytic performance under atmospheric oxygen, even in air. More importantly, the γ-Fe2O3@HAP-Pd(0) catalyst was readily separated from the reaction solution using an external magnetic field and was successfully reused during five consecutive reaction runs while retaining its catalytic effectiveness. This study provides a green and sustainable method for the production of valuable chemicals from renewable resources.

(Bi, C and N) codoped TiO2 nanoparticles.

Bi, C and N codoped TiO2 photocatalysts were prepared by doping TiO2 with BiCl3 and KSCN in a sol-gel process (denoted as (Bi,SCN)-TiO2). The catalyst samples were then characterized by XRD, TEM, diffuse reflectance spectra (DRS), XPS, FT-IR and N2 sorption. Bi, C and N elements were detected both by XPS and elemental analysis, while S element was not found, suggesting that SCN- group may have decomposed during the sol-gel process. The effects of the doping on the properties and photocatalytic activity of the TiO2 were investigated. It was found that the cation and the anion affected the properties of TiO2 differently. The optical absorption onset of TiO2 red shifted in the presence of Bi3+, while long tail occurred in the presence of SCN-. The order of photoreactivity for TiO2 samples was as follow: (Bi,SCN)-TiO2>Bi-TiO2>undoped TiO2>p25 TiO2, whatever under UV or visible light illumination. The high photoreactivity of the doped TiO2 was also discussed.

Two Amino-Decorated Metal–Organic Frameworks for Highly Selective and Quantitatively Sensing of HgII and CrVI in Aqueous Solution

Two amino-decorated metal-organic frameworks have been constructed, which are the rare examples of MOF-based fluorescent probes targeting environmentally relevant guest species, such as Hg (II) and Cr (VI) ions in aqueous solution, with high selectivity and sensitivity. The possible sensing mechanism is also discussed.

Removal of methylene blue from aqueous solutions by chemically modified bamboo

Chemically modified bamboo (CMB) was utilized for removing methylene blue (MB) from aqueous media in the present study. The adsorbent was characterized by Fourier transform infrared (FTIR) spectra and elemental analysis, which confirms that carboxyl groups and diethylenetriamine were successfully introduced into the surface of bamboo. The effects of initial MB concentration (100-900mgL(-1)), contact time (15-315min), the pH of the solution (3-10), temperature (298-318K), adsorbent dosage (0.4-2.6gL(-1)) and salt concentration on the adsorption efficiency of CMB towards MB were investigated. It was found that the adsorption of MB in CMB fits Langmuir mode well, and the maximum adsorption capacity of CMB achieved 606mgg(-1) at 298K, which is much higher than those obtained from previously investigated bioadsorbents. The adsorption kinetics can be described by pseudo-second-order kinetic model, and the adsorption of MB on CMB was an exothermic process. The results of the present study suggest that CMB is an effective biosorbent for removal of organic pollutants from aqueous solutions.

Iron Oxide Encapsulated by Ruthenium Hydroxyapatite as Heterogeneous Catalyst for the Synthesis of 2,5‐Diformylfuran

Magnetic γ-Fe2 O3 nanocrystallites encapsulated by hydroxyapatite (HAP), HAP@γ-Fe2 O3 , were prepared followed by cation exchange of Ca(2+) on the external HAP surface with Ru(3+) to give the γ-Fe2 O3 @HAP-Ru catalyst. The structure of the as-prepared catalyst was characterized, and its catalytic activity was studied in the aerobic oxidation of 5-hydroxymethylfurfural (HMF). γ-Fe2 O3 @HAP-Ru showed a high catalytic activity for the aerobic oxidation of HMF into 2,5-diformylfuran (DFF). A high DFF yield of 89.1 % with an HMF conversion of 100% was obtained after 4 h at 90 °C. Importantly, the synthesis of DFF from fructose was realized by two consecutive steps. The dehydration of fructose in the presence of a magnetic acid catalyst (Fe3 O4 @SiO2-SO3 H) produced HMF in a yield of 90.1%. Then the Fe3 O4 @SiO2 SO3 H catalyst was removed from the reaction solution with a permanent magnet, and HMF in the resulting solution was further oxidized to DFF with a yield of 79.1% based on fructose. The synthesis of DFF from fructose by two steps avoids the tedious separation of the intermediate HMF, which saves time and energy.

A novel magnetic palladium catalyst for the mild aerobic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid in water

In this study, magnetically separable, graphene oxide-supported palladium nanoparticles (C–Fe3O4–Pd) were successfully prepared via a one-step solvothermal route. The C–Fe3O4–Pd catalyst showed excellent catalytic performance in the aerobic oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). The base concentration and reaction temperature significantly affected both HMF conversion and FDCA selectivity. High HMF conversion (98.2%) and FDCA yield (91.8%) were obtained after 4 h at 80 °C with a K2CO3/HMF molar ratio of 0.5. The C–Fe3O4–Pd catalyst was easily collected by an external magnet and reused without significant loss of its catalytic activity. The developed method is a green and sustainable process for the production of valuable FDCA from renewable, bio-based HMF in terms of the use of water as solvent, the use of stoichiometric amount of base, high catalytic activity under atmospheric oxygen pressure, and facile recyclability of the catalyst.

Aerobic oxidation of biomass derived 5-hydroxymethylfurfural into 5-hydroxymethyl-2-furancarboxylic acid catalyzed by a montmorillonite K-10 clay immobilized molybdenum acetylacetonate complex

In this study, we have successfully prepared a heterogeneous catalyst (K-10 clay-Mo) by the immobilization of bis(acetylacetonato) dioxo-molybdenum(VI) [MoO2(acac)2] on montmorillonite K-10 clay. The structure of the resultant catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electronic microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The catalytic activity of K-10 clay-Mo was tested in the aerobic oxidation of 5-hydroxymethylfurfural (HMF). Although a molecule of HMF contains one hydroxyl group and one aldehyde group, to our surprise, the catalyst showed high catalytic activity for the oxidation of the aldehyde group of HMF into 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). A variety of important reaction parameters such as the reaction temperature, catalyst amount, and solvent were explored. HMFCA could be obtained in a high yield of 86.9% with a HMF conversion of 100% after a short reaction time of 3 h in toluene. More importantly, the catalyst K-10 clay-Mo could be reused several times without a significant loss of its catalytic activity.

Transformation of TiOF2 Cube to a Hollow Nanobox Assembly from Anatase TiO2 Nanosheets with Exposed {001} Facets via Solvothermal Strategy

Hierarchical nanostructures have attracted increasing interest due to their exceptional properties and widespread potential applications. In this paper, anatase TiO2 hollow nanoboxes (TiO2-HNBs) are formed by assembly of nanosheets with exposed {001} facets by solvothermal treatment of TiOF2 cubes in alcohols (tert-butanol and ethanol) at 180 °C. It was found that phase transformation of TiOF2 to anatase TiO2 begins at corners and edges of TiOF2 cubes due to in situ hydrolysis of TiOF2, where water was produced by dehydration of alcohol molecules. With extension the reaction time, TiO2-HNB assemblies from nanosheets with exposed high-energy {001} facets were formed due to the steady inside-outside dissolution-recrystallization process. However, the resulting hierarchical TiO2-HNBs are unstable, which can decompose to discrete high-energy TiO2 nanosheets if the reaction time is further extended. The hierarchical TiO2-HNBs show higher photocatalytic activity than discrete high-energy TiO2 nanosheets and P25 TiO2 due to the unique structures of TiO2-HNBs.

Structures, photoluminescence and photocatalytic properties of three new metal–organic frameworks based on non-rigid long bridges

Three new metal–organic coordination polymers, [Cd3(5-NO2-bdc)2(5-NO2-bdcH)2(bpyo)2]n (1), [Mn(5-NO2-bdc)(bbim)]n (2) and {[Gd(5-NO2-bdc)(5-NO2-bdcH)](bpyo)0.5·2H2O}n (3) (5-NO2-bdcH2 = 5-nitro-1,3-benzenedicarboxylic acid; bpyo = 4,4′-bipyridine-N,N′-dioxide; bbim = 1,1′-(1,4-butanediyl)bis(benzimidazole)), were obtained under hydrothermal conditions and characterized structurally. The networks exhibit a variety of topologies and coordination modes at the metal centers. Complex 1 exhibits NaCl-type topology and contains the centrosymmetric trinuclear cluster SBU [Cd3(COO)4O2]. Complex 2 adopts CsCl-type topology based on bimetallic cores and is the first example of compounds containing a cis bbim bridge. Moreover, complex 3 possesses a 3D supramolecular framework by stronger contacts between 2D layers and non-rigid bpyo bridges. The thermal stabilities of 1–3, the photoluminescence properties of 1 as well as the photocatalytic performance of 3 were also examined, and the results indicated that 1 seems to be a good candidate for novel hybrid inorganic–organic photoactive materials, especially, compound 3 represents the rare example of coordination polymers with a 4f metal ion that exhibit good photocatalytic activity for dye degradation under UV light.

High performance of a cobalt–nitrogen complex for the reduction and reductive coupling of nitro compounds into amines and their derivatives

The cobalt–nitrogen catalyst shows high activity for selective reduction of nitro compounds with H2 and other hydrogen donors. Replacement of precious noble metal catalysts with low-cost, non-noble heterogeneous catalysts for chemoselective reduction and reductive coupling of nitro compounds holds tremendous promise for the clean synthesis of nitrogen-containing chemicals. We report a robust cobalt–nitrogen/carbon (Co–Nx/C-800-AT) catalyst for the reduction and reductive coupling of nitro compounds into amines and their derivates. The Co–Nx/C-800-AT catalyst was prepared by the pyrolysis of cobalt phthalocyanine–silica colloid composites and the subsequent removal of silica template and cobalt nanoparticles. The Co–Nx/C-800-AT catalyst showed extremely high activity, chemoselectivity, and stability toward the reduction of nitro compounds with H2, affording full conversion and >97% selectivity in water after 1.5 hours at 110°C and under a H2 pressure of 3.5 bar for all cases. The hydrogenation of nitrobenzene over the Co–Nx/C-800-AT catalyst can even be smoothly performed under very mild conditions (40°C and a H2 pressure of 1 bar) with an aniline yield of 98.7%. Moreover, the Co–Nx/C-800-AT catalyst has high activity toward the transfer hydrogenation of nitrobenzene into aniline and the reductive coupling of nitrobenzene into other derivates with high yields. These processes were carried out in an environmentally friendly manner without base and ligands.