Extending Cyanogel and Prussian Blue Analogue Chemistry to Octacyanometallate-Based Coordination Polymers: Reduced Temperature Routes to Materials Based on Molybdenum and Tungsten

Cyanide coordination polymers (CCPs) and their products made via thermolysis make up a promising class of materials for a variety of energy and analytical applications. While the chemistry of hexacyanometallate-based CCPs is well developed, that of their octacyanometallate [M(CN)₈]^4- (M = Mo, W) analogues is underexplored. This work compares the synthesis, morphology, and thermolytic properties of two types of cyanide coordination polymers: the amorphous [PdCl₄]^2--based cyanogel, Pd-Mo/W, and the nanocrystalline CoCl₂-based Prussian blue analogue, Co-Mo/W. The general decomposition pathways and products for [M(CN)₈]^4--containing polymers are comparable to their hexacyanometallate analogues. All four coordination polymers can be converted to mixed oxide and ternary phosphide systems and generally retain morphology upon heating. Notably, the reduction under inert gas generates alloys in the cyanogel systems and complex reduced mixtures in the Prussian blue analogue (PBA) systems.