Prussian Blue (PB) analogue metal coordination nanocages comprised of mesoporous walls (ca. 3.5 nm pore width) encapsulating a cavity approaching ca. 100 nm in diameter (surfactant free) are presented as an advance in rational metal coordination polymer nanostructure design. The synthesis employs lanthanide ions (Gd(3+) or Er(3+)) which function initially as peripheral coordination crosslinkers of metallo-surfactant templated miniemulsion droplets, and, subsequently, as promoters in the removal of the organic component of those surfactants via metal-assisted ester hydrolysis. The success of this synthetic strategy relies entirely on the periphery coordination event occurring prior to the ester hydrolysis surfactant removal step. Crucially, this one-pot sequential synthesis was achieved using a newly developed metallo-surfactant designed to have a reduced ester hydrolysis rate. Syntheses of this innovative metallo-surfactant, intermediary PB analogue coordination polymer organo-nanoshells and the subsequent conversion to hollow metal coordination nanocages are fully characterised using a wide variety of techniques, including TEM, SEM, EFTEM, EDX, TGA, WAXD, NMR, N(2) adsorption, etc., and represent the first designed synthesis of hollow metal coordination nanocages containing a large nanoscale cavity (wall of hollow nanosphere is mesoporous; hence nanocage).