Recent progress on the frontiers of polyoxometalates structures and applications

Polyoxometalates (POMs),a class of discrete anionic metal oxides in groups V and VI,are constructed via the con- densation of metal oxide polyhedral (MOx,M=W^vI,Mo^vI, Vv,Nb,Ta,etc.and x=4-7)with each other in a comer-, edge-,or rarely in a face-sharing manner [1-3].Up to now, the broadening family of POM derivatives ranges from small size clusters to nanoscale giant aggregates,which have shown impressive chemical and physical properties and great potential in fields of catalysis,magnetism,medicine,photochemistry,environment,energy and materials science [4,5].Latest progress on POMs chemistry is directed to the construction of high-nnclearity clusters and the exploration of functional applications in energy chemistry,catalysis,and self-assembly (Figure 1).

Comparison of the osteogenic capability of rat bone mesenchymal stem cells on collagen,collagen/hydroxyapatite,hydroxyapatite and biphasic calcium phosphate

Collagen(COL),collagen/hydroxyapatite(COL/HA),HA and biphasic calcium phosphate were prepared as representative bone grafting materials with composition analogous to bone,and their structural characteristics were analyzed.The rat bone mesenchymal stem cells(BMSCs)were further seeded onto four groups of materials,and BMSCs grown in basic medium and standard osteogenic medium were set as controls of a reference model to show the basic and osteogenic behavior of cells without the intervention of materials.Cellular behaviors were characterized,including proliferation,spreading morphology and expression of osteogenesis factors.The rat BMSCs proliferated properly with time on four groups of materials as well on two groups of controls,and typical cuboidal,polygonal and extremely-elongated morphologies of cells were observed.According to the real-time polymerase chain reaction data,a higher osteogenic gene expression level was dependent upon the growing morphology but not the proliferation rate of cells,and the osteogenic differentiation capacity of cells onto four groups of materials varied in specific genes.In general,BMSCs exhibited the highest osteogenic capacity onto COL/HA,but the poorest onto HA.The growing behaviors of cells on materials were further discussed in comparison with the cases of OC and BC of the reference model.The present attempt to comparatively analyze cell experimental data with a reference model is expected to be useful for revealing the difference in the osteogenic capability of MSCs onto materials or even the bioactivity of materials.

Polyoxometalates-based heterogeneous catalysts in acid catalysis

Acid catalysis,one of the most important industrial processes,suffers from the toxicity,corrosion and recyclability problems of conventional homogeneous acid catalysts.Thus,the development of green heterogeneous acid catalysts becomes the focus of fundamental research and industrial catalysis.As a class of discrete anionic metal-oxygen clusters with tunable structure at the molecular and atomic scales,polyoxometalates(POMs)benefit from their super strong Br?nsted acidity,high proton mobility,and thermal stability.POMs-based heterogeneous catalysts have been used as the potential green alternatives to conventional homogeneous acid catalysts.In this review,we summarize recent progress on the design strategies of the POMs-based heterogeneous catalysts and their catalytic properties in acid-catalyzed reactions,where they are combined with functionalized cations,modified through covalent interactions,supported onto the non-precious metal support,and introduced into the framework of porous polymers.The design,functional strategies and catalytic performance of these POMs-based heterogeneous catalysts in specific acid-catalyzed reactions are emphasized.