Silylated MgAl LDHs intercalated with MnO2 nanowires: Highly efficient catalysts for the solvent-free aerobic oxidation of ethylbenzene

Abstract A novel method for the preparation of silylated MgAl layered double hydroxides (LDHs) intercalated with MnO 2 nanowires is presented. The method involves functionalizing the calcined MgAl LDHs (LDOs) with mercaptopropyltrimethoxysilane (MPTS), and then treating the silylated LDOs in the aqueous solution of KMnO 4 . The results obtained from XRD, FTIR, ICP, XPS and TEM showed that MPTS could be successfully grafted on LDOs via the reaction between –Si(OCH 3 ) 3 groups on the silane and the –OH groups on LDOs. LDOs grafted with MPTS could reconstruct their original layered structure by treating them in the aqueous solution of KMnO 4 , and in the same time, small amount of MnO 4 − anions were reduced to MnO 2 by the grafted –SH groups on MPTS. The formed small amount MnO 2 could further catalyze the decomposition of MnO 4 − in the interlayers of the reconstructed MgAl LDHs to MnO 2 . The formed MnO 2 was finely dispersed on the LDH support in the form of nanowires (about 1.4 nm in diameter). The MnO 2 /MgAl-LDH composites prepared by this method exhibited high catalytic activity, stability and reusability in the solvent-free aerobic oxidation of ethylbenzene.