For post-synthetic metallation (PSMet) of a metal–organic framework (MOF, [Mn3(L2)(L')] = 1) we show a solvent dependency for the form of the metallated product. PSMet of 1 with MnCl2 in ethanol leads to a single metal entity per coordinating site while acetonitrile yields a remarkably complex multiply metallated product; thus, determining the extent of metallation requires an intimate understanding of the chemistry occurring in the MOF pores.