Water-soluble poly(3-hydroxyalkanoate) containing ionic groups were designed by two successive photoactivated thiol-ene reactions. Sodium-3-mercapto-1-ethanesulfonate (SO3-) and poly(ethylene glycol) (PEG) methyl ether thiol were grafted onto poly(3-hydroxyoctanoate-co-3-hydroxyundecenoate) PHO(67)U(33) to introduce both ionic groups and hydrophilic moieties. The grafted copolymers PHO(67)SO3-(20)PEG(13) were then used as biocompatible coatings of nano-metal organic frameworks (nanoMOFs) surfaces. Scanning electron microscopy and scanning transmission electron microscopy coupled with energy dispersive X-ray characterizations have clearly demonstrated the presence of the copolymer on the MOF surface. These coated nanoMOFs are stable in aqueous and physiological fluids. Cell proliferation and cytotoxicity tests performed on murine macrophages J774.A1 revealed no cytotoxic side effect. Thus, biocompatibility and stability of these novel hybrid porous MOF structures encourage their use in the development of effective therapeutic nanoparticles.