Metal-directed self-assembly has been applied to prepare supramolecular coordination polygons which adopt tetrahedral (1) or trigonal disklike topologies (2). In the solid state, 2 assembles into a stable halide-metal-organic material (Hal-MOM-2), which catalyzes H2O oxidation under photo- and electrocatalytic conditions, operating with a maximum TON = 78 and TOF = 1.26 s-1. DFT calculations attribute the activity to a CoIII-oxyl species. This study provides the first account of how CoII imine based supramolecules can be employed as H2O oxidation catalysts.