A novel “tunnel-like” cyclopalladated arylimine catalyst immobilized on graphene oxide nano-sheet†
A novel “tunnel-like” cyclopalladated arylimine was prepared and immobilized on graphene oxide nano-sheet to form a hybrid catalytic material (denoted as F-GO-Pd) by self-assembly. The F-GO-Pd catalyst was characterized by XRD, FTIR, Raman, XPS, SEM, and TEM. This novel hybrid catalytic material was proven to be an efficient catalyst for the Suzuki–Miyaura coupling reaction of aryl halides (I, Br, Cl) with arylboronic acids in aqueous media under mild conditions with a very low amount of catalyst (0.01 mol%) and a high turnover frequency (TOF) (>20 000 h−1). In particular, high yields also could be obtained at room temperature with prolonged time. F-GO-Pd also showed good stability and recyclability seven times with a superior catalytic activity. The heterogeneous catalytic mechanism was investigated with kinetic studies, hot filtration tests, catalyst poisoning tests, and in situ FTIR spectroscopy with a ReactIR and the deactivation mechanism of the catalysts was proposed through analysis of its chemical stability by TEM, SEM, Raman, and XRD, indicating that a heterogeneous catalytic process occurred on the surface and the changes of the catalytic activity during the recycling were related to the micro-environment of the catalyst surface.