From an Octakis(3-cyanopropyl)silsesquioxane Building Block to a Highly COOH-Functionalized Hybrid Organic–Inorganic Material

A new nanostructured and highly COOH-functionalized hybrid organic–inorganic material has been synthesized by the hydrolysis of oligomeric octahedral silsesquioxane (POSS), which contains eight cyanopropyl groups. The hybrid, elemental building block oligomeric octakis(3-cyanopropyl)silsesquioxane (CN-POSS) was synthesized from oligomeric octakis(3-chloropropyl)silsesquioxane (Cl-POSS) by an exchange reaction. The formation and nanostructuration of the COOH-functionalized hybrid material were induced by noncovalent hydrogen bonding between COOH-POSS units without decomposition of the core. The material has been fully characterized by scanning electron microscopy, FTIR and 1H, 13C, and 29Si solid-state NMR spectroscopy, X-ray diffraction, and elemental analysis, which confirm that the POSS core remains intact after each chemical modification step. Thermogravimetric analysis indicates that the organic units are thermally stable up to 200 °C. The activation energy related to the proton conductivity of COOH-POSS has been evaluated and confirms the presence of strong hydrogen bonds. Finally, the accessibility and adsorption capacity of the COOH groups towards transition metal ions have been demonstrated and underline the potential of these hybrid materials in extraction chemistry.