Versatile methods for the formation of porous metal and nanoparticles from cyanometalate coordination polymers

Cyanogels are an inorganic sol-gel system that is based on an amorphous cyanide bridged transition metal polymer that results from the polymerization of a chlorometalate and cyanometalate in aqueous solution. Cyanogels can be used to produce a variety of materials including metal alloys as the cyanogel polymer will auto-reduce at elevated temperatures to form metal alloys in an inert atmosphere. This work expands the versatility of the cyanogel system by focusing on the development and control of the final morphology of materials derived from cyanogels. A facile two-step synthetic route to macroporous metal and metal alloy frameworks from the cyanogel hydrogel is described. Cyanogels are versatile precursors to macroporous metals due to the large number of metal alloy systems that can be produced. This synthetic route is advantageous due to the production of uncontaminated final products of refractory metals at low temperatures. Transient reactive liquid sintering is shown to be the physical process through which macroporous metal forms from the cyanogel precursor.;Nanoparticles of the cyanogel system are isolated by several means including solvent alteration and counter-ion metathesis. The nanoparticles isolated by counter-ion metathesis are stable, soluble in organic solvents such as dichloromethane and have an average diameter of 4 +/- 1 nm (mean +/- sd). The synthesis of nanoparticles is amenable to a variety of transition metals as Pd-Co, Pd-Ru and Pd-Fe cyanometalate polymer nanoparticles are isolated. Increasing the reaction time prior to counter-ion exchange allows for the isolation of nanoparticle agglomerates of various sizes. The transition metal ratio of the nanoparticulate polymer network is demonstrated to be under synthetic control. Subsequent chemical alteration of the nanoparticles is afforded due to the free coordination sites of the transition metals in the polymer. The nanoparticles also serve as chemical precursors to transition metal alloy nanoparticles due to the ability of bridging cyanides to act as reducing agents at relatively low temperatures.