The solvent-free chemical fixation of carbon dioxide with glycidyl ether functionalized polyhedral oligomeric silsesquioxanes (FOSS) yields mono- and polydisperse multifunctional BOSS cyclic carbonates. The silica equivalent content of POSS carbonates varies between 28.5 and 42.1 wt %, whereas 15.4-20.8 wt % carbon dioxide is incorporated. On cure with hexamethylenediamine and isophoronediamine, FOSS carbonates and their blends with polyol-based cyclic carbonates produce organic/inorganic hybrid polyhydroxyurethane thermosets without requiring the need of isocyanate monomers. These blends prolong both gel and pot life time of NIPU formulations, thus allowing the preparation of tailored NIPU/POSS hybrid materials for casting and coating applications. Young's modulus and tensile strength improve with increasing FOSS content as a result of higher cross-link density and silica content. Submicron phases are formed during polymerization due to self-assembly and nanophase separation as was verified by scanning electron microscopy (SEM). Moreover, the incorporation of FOSS significantly improves scratch resistance of optically transparent and colorless NIPU/POSS coatings as examined by the surface gloss and SEM images.