Artificial nacre based on polydopamine functionalized graphene oxide nanosheets constrained palladium nanocluster with enhanced mechanical properties and catalytical functionalities.

Inspired by "the composition of catechol and amine groups in the adhesive proteins" of marine mussel and "brick-and-mortar" structure of nacre, we use polydopamine (PDA) as "mortar", graphene oxides (GO) nanosheets as "brick", and Pd2+ ions as interfacial reinforcer, to fabricate nacre-like Pd2+ enhanced PDA functionalized GO membranes (Pd@PDA/GO) with vacuum filtration-assisted assembly method. Meanwhile, in situ reduced Pd0 nanoclusters by PDA chains were well constrained within the resultant Pd@PDA/GO artificial nacre composites. Good interfacial adhesion with dense packing of the GO nanosheets was further confirmed with sub-nano level microstructure characterization by positron annihilation lifetime spectroscopy. The microstructural evolution of the laminated composites has been probed in depth from a theoretical computational point of view using molecular dynamics (MD) simulations. The optimal Pd@PDA5/GO95 artificial nacre composite exhibits highest tensile strength of 151.6 MPa, about three times of staring GO membranes. Using as low as 0.03 mol% of Pd@PDA5/GO95 catalyst, Suzuki coupling reaction of aryl halides with phenylboronic acid can be efficiently catalyzed and recycled for 6 runs with excellent yield.