AbstractThe three-dimensionally ordered macroporous alumina-carbon composite materials were firstly prepared through a surfactant-assisted colloidal crystal template method and applied to support Pt nanoparticles. The results of SEM, XRD, TEM, and N2 sorption analyses revealed that these composite materials possessed highly ordered macroporous structures with meso- and micropores within the skeletons of macropores and that the Pt nanoparticles were well dispersed on these materials with a very narrow size distribution. These prepared Pt nanocatalysts were evaluated in the asymmetric hydrogenation of ethyl pyruvate after chiral modification with cinchonidine. Excellent catalytic activity and enantioselectivity were achieved. More importantly, these catalysts exhibited extraordinary stability and reusability during the reaction and could be reused at least 26 times without significant loss in catalytic activity and enantioselectivity.

In this paper, the selective hydrogenation of halonitrobenzenes (HNBs) to haloanilines (HANs) under mild conditions catalyzed by well-dispersed Pt nanoparticles protected by thiol-terminated poly(N-isopropyl acrylomide) (PNIPAM-SH) was firstly investigated. The polymer not only protected the Pt nanoparticles, but also inhibited the highly active Pt catalyst from producing undesired hydrodehalogenation products through anchoring the thiol groups to the surface of Pt nanoparticles. Thus high selectivities to HANs were achieved over this modified Pt catalyst for a variety of HNBs with satisfactory catalytic activities. Especially, the selectivity to HANs showed no obvious loss with the prolonging of the reaction time. Moreover, the recycling experiment showed that this Pt nanocatalyst was easier to recover and reuse based on the cononsolvency of PNIPAM-SH. Excellent stability and reusability were presented over this catalyst, and both the catalytic activity and selectivity were well maintained after fourteen runs.