Synthesis and application of nanoporous triple-shelled CuAl2O4 hollow sphere catalyst for atmospheric chemical fixation of carbon dioxide.

• The successful synthesis of a nanoporous triple-shelled CuAl2O4 hollow sphere was developed. • Novel CuAl2O4 structure was active for CO2 cycloaddition of epoxides at atmospheric pressure. • The reaction could be performed under solvent-free conditions. • Proposed catalyst is suitable for direct conversion of CO2 in post combustion exhaust gas directly. Designing complex hollow nano-/microspheres with multilayered structures of two or more metal oxides seems to be interesting to answer the request for novel catalytic structures. Herein, we develop a copper-alumina spinel hollow sphere with a triple-shell structure applied as a novel catalyst for the cycloaddition of CO 2 at atmospheric pressure. Different operating conditions such as reaction temperature, various solvents and reaction time were studied in this reaction. Besides, different epoxides were converted at 80°C, under bubbling of CO 2 at atmospheric pressure, a catalyst loading of 3 wt.% and a reaction time of 24 h with isolated yields up to 100% of the carbonate. In addition, the kinetics of the reaction was investigated at different reaction temperatures by calculating the reaction rate constant and activation energy (based on the Arrhenius equation). The nanoporous triple-shell CuAl 2 O 4 hollow microspheres reduce the mass transfer path of different reactant and product molecules along with better accessibility of interior active sites that improves the catalytic efficiency with suitable activity and remarkable cycling stability. [ABSTRACT FROM AUTHOR]