We have used X-rays to study the structure of photomagnetic, heterostructured films of nickel hexacyanochromate and cobalt hexacyanoferrate Prussian blue analogs on poly(ethylene terephthalate) solid supports. The nature of the interface between supporting polymer and Prussian blue analog is investigated and either positive or negative ions will bind to the surface depending upon pre-treatment. For heterostructured films fabricated using layers of a few hundred nanometers, each layer retains a crystal structure similar to that in the homogeneous phase, while heterostructured films that layer nanometer scale layers result in a solid solution of the two compounds that may have bond deformation. Regardless of layering thickness, these sequential adsorption films are polycrystalline. ► We have synthesized tri-layered heterostructures of Prussian blue analogs. ► Different solid support pretreatment bonds either cations or anions from the network. ► Films are polycrystalline having the same crystal structures as parent phases. ► Structure probes suggest bond-length deformation in mixed phase films.