Silver Linked Polyoxometalate Open Frameworks (Ag-POMOFs) for the Directed Fabrication of Silver Nanomaterials

A design approach for the preparation of the {(DMAH)7[H2SbW18O60]} (DMAH-2) and {(DMAH)7[H2BiW18O60]} (DMAH-3) (DMAH = dimethylammonium) systems in a highly pure crystalline form is presented, and the latter is characterized by electrospray ionization mass spectrometry (ESI-MS) methods for the first time. These, together with the archetypal [W10O32] cluster, are used as precursors for the formation of unique framework materials incorporating Ag(I) as a linking species. The systems are fully characterized by X-ray crystallography, elemental analysis, IR and thermogravimetric analysis (TGA), and the pyrolysis of the {Ag4-W10O32} system (1) leads to the formation of silver microparticles embedded in the resulting tungsten oxide and this has been observed by us previously with other systems. In contrast, the carefully controlled decomposition of the antimony and bismuth systems {Ag418O60} (Ag-2) and {Ag4-SbW18O60} (Ag-3) gives rise to the formation of highly pure, discrete silver microparticles as confirmed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analysis. These unique materials may be interesting for applications such as catalysis, antimicrobial agents, or electroactive/photoactive coatings, and this work demonstrates how the molecular organization of the building blocks on the nanoscale can affect the assembly of materials over a range of length scales.