Guowu Zhan

Mesoporous Bubble‐like Manganese Silicate as a Versatile Platform for Design and Synthesis of Nanostructured Catalysts

Manganese silicate in bubble-like morphology was used as a versatile platform to prepare a new class of yolk-shell hybrids. The mesoporosity of the shell was generated from the interbubble space and the bubble structure of manganese silica was used to hold and support nanoparticles (e.g., Au, Ag, Pt, Co, Ni, Au-Pd alloy, MoO2 , Fe3 O4 , carbon nanotubes and their combinations). We also used heterogeneous catalysis reactions to demonstrate the workability of these catalysts in both liquid and gas phases.

Smart Nanocatalysts with Streamline Shapes

Particulate catalysts with streamline shapes have important impacts on fluid-related reactions, and they need to be properly characterized. However, utilization of streamline-shaped catalysts for heterogeneous catalysis has remained an unexplored area due to the lack of easy-to-use techniques to produce such shaped catalysts, especially at the small length scale of the submicron to micron regime. Herein, we report our recent development of a class of prototype nanocatalysts with streamline shapes. In this research, the kinetic control is adapted to obtain streamline-shaped supports, followed by functionalizing such supports with catalytically active metal nanoclusters (e.g., Au, Pd, Pt, and Ag or their combinations) in a stepwise manner. Advantages related to the streamline morphology of catalysts have been demonstrated with a number of solid-solution systems such as alcohol oxidation, olefin hydrogenation, and Suzuki-Miyaura coupling. We believe these findings will promote new research on the design and synthesis of functional materials with additional fluid-advanced features.

Topological Transformations of Core–Shell Precursors to Hierarchically Hollow Assemblages of Copper Silicate Nanotubes

Functional hollow materials have attracted extensive research attention due to their promising prospects for catalysis. Herein, we report an alternative synthesis of hierarchically hollow structured materials directly from core-shell structured templates, based on confined chemical reactions between the solid matter of a core and shell under hydrothermal conditions. More specifically, we have developed a novel and facile strategy to transform core-shell structured Cu2O@mSiO2 (m = mesoporous) to tubular copper silicate assemblages (TCSA). Depending on the original shapes of Cu2O, TCSA can be tailored as spherical or cubic assemblages with stacking copper silicate nanotubes (inner diameter: 4.5 nm, thickness: 0.8 nm, length: ca. 96 nm) in the shell. Moreover, by utilizing the residual reductive Cu(I) (ca. 10 at% of total surface copper) on TCSA support, in situ generations of Pd nanoparticles (∼4.5 nm) and Au nanoparticles (∼5.8 nm) were successfully achieved based on the spontaneous galvanic replacement reactions. Two integrated nanocatalysts (viz., Pd/TCSA and Au/TCSA) have been prepared with this approach. As an example, Pd/TCSA exhibits excellent activity and recyclability for Suzuki-Miyaura cross-coupling reactions.