Abstract
Four vinyl polymer gels (VPGs) were synthesized by free radical polymerization of divinylbenzene, ethane-1,2-diyl dimethacrylate, and copolymerization of divinylbenzene with styrene, and ethane-1,2-diyl dimethacrylate with methyl methacrylate, as supports for palladium nanoparticles. VPGs obtained from divinylbenzene and from divinylbenzene with styrene had spherical shapes while those obtained from ethane-1,2-diyl dimethacrylate and from ethane-1,2-diyl dimethacrylate with methyl methacrylate did not have any specific shapes. Pd(OAc)2 was impregnated onto VPGs and reduced to form Pd0 nanoparticles within VPGs. The structures of Pd0-loaded VPGs were analyzed by XRD, TEM, and nitrogen gas adsorption. Pd0-loaded VPGs had nanocrystals of Pd0 within and on the surface of the polymeric supports. Pd0/VPGs efficiently catalyzed the oxidation/disproportionation of benzyl alcohol into benzaldehyde/toluene, where activity and selectivity between benzaldehyde and toluene varied, depending on the structure of VPG and the weight percentage loading of Pd0. The catalysts were stable and Pd leaching to liquid phase did not occur. The catalysts were separated and reused for five times without any significant decrease in the catalytic activity.
Highlights
Metal nanoparticles (MNPs) are an important class of catalysts [1,2]
Palladium has been most widely studied for many organic reactions including oxidation [3,4,5,6,7], reduction [8,9,10], hydrogenation [11,12], and cross coupling reactions [13,14,15,16,17], gas adsorption/release applications [18,19], and biological applications [20]
porous organic polymers (POPs) may be constructed with much wider structural variations, based on a large range of polymer structures that can be synthesized from various types of monomers through well-established polymerization methods
Summary
Metal nanoparticles (MNPs) are an important class of catalysts [1,2]. Among various metals, palladium has been most widely studied for many organic reactions including oxidation [3,4,5,6,7], reduction [8,9,10], hydrogenation [11,12], and cross coupling reactions [13,14,15,16,17], gas adsorption/release applications [18,19], and biological applications [20]. MNPs generally exhibit high activities; particle leaching and agglomeration can lead to decline in their performance [17] These problems can be circumvented by the use of solid supports, including inorganic materials such as zeolite [21], silica gel [22], metal oxide [23,24], carbide-modified Pd on ZrO2 [25], activated carbon [26], porous carbon [27]. Inorganic supporting materials loaded with MNPs perform well in general, their structural variants are rather limited [29] Organic materials such as porous organic supports have been investigated and, porous organic polymers (POPs) [30,31,32]. Among other examples of nonpolymeric porous organic supports, an exotic one is a hybrid porous solid support for
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