Efficient Conversion of Carbon Dioxide by Imidazolium‐Based Cross‐Linked Nanostructures Containing Polyhedral Oligomeric Silsesquioxane (POSS) Building Blocks

• Published in: ChemPlusChem (Weinheim, Germany) Germany), 2019-10, Vol.84 (10), p.1536-1543
• Main Authors: Calabrese, Carla, Fusaro, Luca, Liotta, Leonarda Francesca, Giacalone, Francesco, Comès, Adrien, Campisciano, Vincenzo, Aprile, Carmela, Gruttadauria, Michelangelo
• Format: Article
• Language: English
• Subjects: carbon dioxide conversion; cyclic carbonates; heterogeneous catalysis; imidazolium salts; polyhedral oligomeric silsesquioxanes
• ISSN: 2192-6506; 2192-6506
• DOI: 10.1002/cplu.201900408

Polyhedral oligomeric silsesquioxanes (POSS) have been employed as molecular building blocks for the synthesis of imidazolium cross‐linked networks, to be used as heterogeneous catalysts for the conversion of carbon dioxide into cyclic carbonates. Two hybrid materials with different nucleophilic species (bromide and iodide) have been prepared and characterized by means of elemental analysis, 13C and 29Si solid‐state NMR spectroscopy, thermogravimetric analysis and IR spectroscopy. The solids were tested as the sole catalyst under metal‐ and solvent‐free reaction conditions showing full selectivity toward the formation of cyclic carbonates. High turnover number (TON) and productivity values, up to 5502 and 1081 respectively for glycidol conversion at 100 °C and up to 4942 and 1122 for epichlorohydrin conversion at 150 °C after 3 h, were obtained. Such outstanding productivity values were ascribed to the optimal organic/inorganic (i. e., imidazolium moiety/POSS support) weight ratio. The recyclability of the materials was successfully verified for five consecutive runs allowing their consideration as promising candidates for continuous flow technologies. Fast, simple and high‐yielding synthesis of polymeric cross‐linked imidazolium‐POSS materials for the efficient conversion of carbon dioxide and epoxides into cyclic carbonates has been achieved. Cyclic carbonates have been obtained with high TON and productivity values, up to 5502 and 1081 respectively for glycidol at 100 °C and up to 4942 and 1122 for epichlorohydrin at 150 °C.