Qingshan Zhao

Palladium Complex Immobilized on Graphene Oxide as an Efficient and Recyclable Catalyst for Suzuki Coupling Reaction

A graphene supported palladium (Pd) catalyst for Suzuki coupling reaction has been successfully prepared by immobilizing Pd(II) onto graphene oxide surface through the in situ coordination interaction with aminosilane ligand spacers. This catalyst showed high catalytic activities in the Suzuki coupling of various aryl halides and phenylboronic acid. Moreover, it could be readily recycled and reused for several times without discernible loss of its catalytic activity.Graphical Abstract

Enhanced hydrogenation of olefins and ketones with a ruthenium complex covalently anchored on graphene oxide

Graphene oxide (GO) is a promising support for anchoring homogeneous metal complexes because of its two-dimensional structure, huge surface area and diversity for chemical functionalizations. In this study, a ruthenium supported catalyst has been synthesized by covalently bonding a ruthenium complex (RuCl2(PPh3)3) onto the GO surface through coordination interaction with aminosilane ligand spacers. The supported catalyst showed enhanced catalytic performance towards hydrogenation of olefins and ketones compared with the homogeneous analogue, and it could be readily recycled and reused several times without discernible loss of its activity.

Combining palladium complex and organic amine on graphene oxide for promoted Tsuji–Trost allylation

In this study, we develop a facile strategy to combine an organic amine with a palladium complex on graphene oxide (GO) as a cooperative catalyst for Tsuji–Trost allylation. A tertiary amine and palladium–diamine complex are simultaneously immobilized on a GO support through silylation and further in situ coordination processes. PdCl2 is employed as the palladium precursor, with no necessity for extra coordination ligands. Various characterizations confirm the successful preparation of the cooperative supported catalyst (GO–NEt2–2N–Pd). Systematic investigation reveals the immobilized palladium–diamine complex (GO–2N–Pd) with very low Pd loading is effective for Tsuji–Trost allylation, and incorporation of the tertiary amine shows a significant promoting effect towards the catalytic activity. GO–NEt2–2N–Pd can be readily recovered and recycled several times without reduction of its efficiency. Its excellent performance should be ascribed to synergistic catalysis effect, excellent support properties, and robust immobilization interaction.

Cooperative catalysis by acid–base bifunctional graphene

Acid–base bifunctional catalysts are of particularly interest, but also present great challenges in synthesis and applications. In this study, acid–base bifunctional graphene oxide hybrids were obtained by the modification of graphene oxide (GO) through a silylation reaction and radical addition. The obtained bifunctional hybrids displayed high acid and base catalytic activities towards a typical one-pot acid–base reaction sequence called deacetalization–nitroaldol reaction.

Exfoliated MoS2 supported Au–Pd bimetallic nanoparticles with core–shell structures and superior peroxidase-like activities

Au–Pd bimetallic nanoparticles (NPs) with core–shell structures have been successfully anchored on chemical exfoliated MoS2 (Au–Pd/MoS2) through a facile co-reduction method at room temperature. The Au–Pd/MoS2 hybrids were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The pristine MoS2 nanosheets exhibit some peroxidase-like activity for the oxidation of 3,3,5,5-tetramethylbenzidine (TMB), and their catalytic activity is significantly enhanced by the deposition of Au–Pd NPs. A systematic study revealed that Au–Pd NPs with a mass ratio of 1 : 2 on MoS2 (Au1.0Pd2.0/MoS2) showed the highest catalytic activity compared with other counterparts. This excellent performance of the Au1.0Pd2.0/MoS2 hybrids should be ascribed to not only the intrinsic catalytic activity of MoS2, but also the complicated metal–metal and metal–support interactions.

Thermo-sensitive graphene supported gold nanocatalyst: synthesis, characterization and catalytic performance

Graphene has attracted increasing attention as a support for heterogeneous catalysis. Although successful preparation and excellent catalytic performance of many graphene based nanocatalysts have been demonstrated, graphene supported nanocatalysts with turnable catalytic behaviors remain unexplored. In this study, we report a strategy to prepare a graphene supported Au nanocatalyst with thermo-sensitive catalytic behaviors. This smart catalytic system was prepared by introducing the temperature-responsive poly(N-isopropylacrylamide) (NIPAAm) and Au nanoparticles to graphene oxide (GO) through reversible addition–fragmentation chain transfer polymerization and direct co-reduction of HAuCl4. The obtained GO–NIPAAm–Au hybrid was systematically characterized and showed interesting thermo-sensitive catalytic activity in the catalytic reduction of 4-nitrophenol.

Gold nanoparticles supported on layered TiO2–RGO hybrid as an enhanced and recyclable catalyst for microwave-assisted hydration reaction

In this study, we synthesized a novel composite material (Au–TiO2–RGO) consisting of tiny gold nanoparticles (∼4.5 nm) grown on a layered titania (TiO2) and reduced graphene oxide (RGO) hybrid. After treatment with microwave and sulfuric acid, solid acid (SO42−/TiO2) was in situ formed on the surface of TiO2, and the resulting Au–SO42−/TiO2–RGO was determined as an enhanced catalyst for hydration reaction. The strong metal-support interaction (SMSI) between Au and TiO2 and the cooperative effect between Au and SO42−/TiO2 solid acid collectively account for the excellent performance. Moreover, due to the versatile RGO substrate, the catalyst could also be recycled and reused at least 5 times without obvious deactivation.

Graphene Supported Pt/Ni Nanoparticles as Magnetically Separable Nanocatalysts

Efficient recovery of nanocatalysts, especially the graphene supported noble metal catalysts, is a challenge. In this study, we report a simple one-step route to prepare the graphene supported Pt/Ni nanocatalysts with ideal superparamagnetic properties. We demonstrated that they had excellent catalytic activities in the catalytic reduction of aromatic nitro compounds and could be easily separated from the reaction mixtures by applying an external magnetic field.

Controllable Preparation of Ultrathin Sandwich-Like Membrane with Porous Organic Framework and Graphene Oxide for Molecular Filtration.

Porous organic frameworks (POFs) based membranes have potential applications in molecular filtration, despite the lack of a corresponding study. This study reports an interesting strategy to get processable POFs dispersion and a novel ultrathin sandwich-like membrane design. It was accidentally found that the hydrophobic N-rich Schiff based POFs agglomerates could react with lithium-ethylamine and formed stable dispersion in water. By successively filtrating the obtained POFs dispersion and graphene oxide (GO), we successfully prepared ultrathin sandwich-like hybrid membranes with layered structure, which showed significantly improved separation efficiency in molecular filtration of organic dyes. This study may provide a universal way to the preparation of processable POFs and their hybrid membranes with GO.