Palladium nanoparticles captured in microanotextured porous polymers: A tailor-made catalyst for heterogeneous carbon cross-coupling reactions

摘要

Palladium nanoparticles (PdNPs) supported on insoluble solids are materials of considerable current interest in fundamental scientific fields as well as in environment-friendly catalytic applications. This is based on the advantages of PdNPs, which includes both the intrinsic versatility of Pd metals as a catalyst and the specific size effect of nanoparticles: that is, a large surface-to-volume ratio. In this study, we focused on the fact that radicals at growing polymer chains are responsible for reduction of Pd ions. On the basis, when the polymer radical reduction system was applied for the polymerization-induced phase separation (PIPS) setup of cross-linkable monomer/porogenic solvent mixtures, PdNPs captured in microanotextured porous network polymers were successfully obtained in one-pot convenient procedure. This system is enabled to avoid the rapid Pd reduction by additional reducing reagents and therefore has an advantage, that is, easy control in particle size and crystallinity of being created PdNPs. The resultant polymer was found to have a mesoporosity; the nitrogen sorption analysis gave a specific-surface area of 510 m2 g.1, an average pore diameter of 9.9 nm, and a total pore volume of 1.01 mL g.1. The TEM images of the polymer revealed that the created PdNPs were very small with a diameter of ca. 2.0 nm; the high resolution images were lattice-resolvable (Pd(111) facets were clearly detected). The PdNPs-containing microanotextured porous polymer was demonstrated to be a highly active catalyst for heterogeneous aqueous carbon cross-coupling reactions, with intriguing characteristics of high turnover number and easy recyclabilities.