Poly(ionic liquid)s hollow spheres nanoreactor for enhanced cyclohexane catalytic oxidation

• Hollow sphere structure of poly(ionic liquid)s (HPILs) was fabricated as nanoreactor. • HPILs nanoreactor efficiently enhanced the activity of metal catalysts and showed high selectivity of AA. • HPILs could storage and stabilize catalysts during reaction with high activity for 7 times. • HPILs could promote the generation of free radicals to enhance the reaction. • The reaction process of HPILs was theoretically calculated to verify high activity and selectivity. Hollow structure nanoreactors take advantage of catalyst loading and enhanced activity by shell construction. In this work, functionalized poly(ionic liquid)s (PILs) with hollow spherical structures were synthesized by polymerization- and quaternization-based approaches. These hollow structure PILs (HPILs) could be controllable designed from IL monomer easily, giving HPILs various properties. In the subsequent selective oxidation of cyclohexane , the HPILs acting as nanoreactors could efficiently improve the activity of metal salt catalysts (CoCl 2 ) and displayed adjustable selectivity for cyclohexanone, cyclohexanol (KA) or adipic acid (AA) by different types of HPILs. In kinetic study , it follows first-order reaction kinetics which CoCl 2 /HPIL-C12 had a lower the activation energy of 29.1 kJ/mol. Importantly, these nanoreactors storing the catalysts could be recovered and reused more than 7 times without significant loss of activity. A theoretical model for the hollow spherical reactor was further established to support the advance of the HPILs reactor, which could also help to predict reaction process in other core-shell catalytic system. Due to controlled substrate transfer and enhanced radical generation in HPILs, the reaction process could be adjusted to enhance the conversion of cyclohexane and selective oxidation to AA.