Imidazolyl‐Functionalized Ordered Mesoporous Polymer from Nanocasting as an Effective Support for Highly Dispersed Palladium Nanoparticles in the Heck Reaction

Abstract

New imidazolyl‐functionalized ordered mesoporous cross‐linked polymers were prepared by the copolymerization of the ionic liquid 3‐benzyl‐1‐vinyl‐1H‐imidazolium bromide with divinylbenzene as the cross‐linker and azobisisobutyronitrile as the radical initiator in the presence of O‐silylated SBA‐15 as the hard template. The materials were characterized by N2 adsorption–desorption analysis, TEM, thermogravimetric analysis, elemental analysis, and FTIR spectroscopy. The material, which benefits from the use of entrapped ionic liquid in the prepared polymer matrix in combination with its ordered mesoporous structure, is an excellent environment for the stabilization of highly dispersed Pd nanoparticles to result in a recyclable catalyst system with a significant activity in the Heck coupling reaction of aryl halides. The presence of well‐distributed imidazolium functionalities in the polymeric framework might be responsible for the relatively uniform and nearly atomic scale distribution of Pd nanoparticles throughout the mesoporous structure and the prevention of Pd agglomeration during the reaction, which results in high durability, high stability, and good recycling characteristics of the catalyst. Although our catalyst system operates in a homogeneous pathway, it is also very stable and recyclable.

Nanopalladium on Magnetic Ionic Nanoparticle Network (MINN) as an Efficient and Recyclable Catalyst with High Ionic Density and Dispersibility

“…Although it is not possible at this stage to provide the exact mechanism for the partial reduction of Pd­(II) ions, it might be concluded that the high organic content of imidazolium rings in the developed system is responsible for this phenomenon. It should be noted that we recently found the same observation in the immobilization of Pd ion (as a counterion of ionic liquid) in the pores of an ionic liquid containing mesoporous polymer . Since detecting the Pd species in the TEM image of the catalyst is not possible due to difficulty in distinguishing the iron oxide and Pd nanoparticles in the TEM image, we also prepared a map scan survey from the fresh catalyst to clarify the presence of Pd species.…”

“…It should be noted that we recently found the same observation in the immobilization of Pd ion (as a counterion of ionic liquid) in the pores of an ionic liquid containing mesoporous polymer. 52 Since detecting the Pd species in the TEM image of the catalyst is not possible due to difficulty in distinguishing the iron oxide and Pd nanoparticles in the TEM image, we also prepared a map scan survey from the fresh catalyst to clarify the presence of Pd species. The map scan image from the surface of the catalyst confirmed the presence of Pd species and their good distribution across the support (Figure S18).…”

Polystyrene-Supported Acyclic Diaminocarbene Palladium Complexes in Sonogashira Cross-Coupling: Stability vs. Catalytic Activity

“…Recently, the focus of the research on the cross-coupling reactions has shifted towards the development of not only efficient methods, but also sustainable and economical processes that employ heterogeneous systems [14][15][16]. Currently, there are several reports on the development of heterogeneous catalysts obtained by the immobilization of NHC-Pd [17][18][19][20] on polystyrene [21][22][23][24][25], silica gel [26,27], silicon oxide-based mesoporous materials [28][29][30][31], nanomagnetite [32,33] and graphene oxide [34][35][36]. The general approach for the NHC-Pd immobilization is based on the reaction between the Pd source (Pd(OAc) 2 or PdCl 2 ) and imidazolium salt, which is covalently attached to the surface of the solid support.…”

Applications of SBA-15 supported Pd metal catalysts as nanoreactors in C–C coupling reactions

“…30 Mesoporous SBA-15 based Pd catalysts have developed some of the most interesting catalytic elds in organic synthesis, partially in different types of carbon-carbon coupling reactions. 31,32 As SBA-15 possess large specic surface area containing highly ordered two-dimensional (2D) hexagonal mesostructure, it can be used for capturing of Pd complexes. Besides, the capturing decreases the leaching of Pd species into the solution, which is a usual problem associated with other Pd supported catalysts.…”