The interfacial topology of block copolymer cubic mesophases opens only one of two internal water channel networks for diffusion. Utilizing this topology selection, single and double diamond cubic crystalline networks of Ni were synthesized from cubic block copolymer (BCP) mesophase templates via electroless plating, in which the lattice structures were converted to the polymer cubosome (PC) internal pore networks by selective metal-ion diffusion. This was accomplished by manipulating the BCP molecular weight, which consequently allowed for selective access to the PC internal pore networks. This work provides a selective protocol for highly defined transition-metal cubic networks that are suitable for application in catalysis, electrochemistry, and synthesis of metamaterials with photonic and magnetic properties.