Insights into the catalytic activity and recyclability of Pt deposited on PDA encapsulated porous silica toward hydrosilylation reaction

Mussel inspired polydopamine (PDA) has been extensively applied as a linker in noble metal based heterogeneous catalysts to promote either metal dispersion or metal-support interaction. Herein, three heterogeneous Pt catalysts were first prepared by depositing Pt on PDA encapsulated porous silica (SiO 2 -PDA-Pt) with different PDA coating degree and their catalytic activity toward two model hydrosilylation reactions between methyldichlorosilane and a non-polar 1-octene and a polar allyl cyanide were investigated. Meanwhile, stability and recyclability of these catalysts were also explored. Results show that PDA coating degree may directly influence both Pt loading and its oxidation state, which then resultantly tailor the activity of the supported catalysts. The SiO 2 -PDA-Pt catalysts all showed excellent activity even after six catalytic rounds even though a gradual loss of Pt species were observed. Among them, the activity of the one with lowest PDA coating exhibited both higher activity and better recyclability, which is mainly ascribed to a higher content and retention of more active low valent Pt 0 species that may be well stabilized by proper PDA coating.