Light-controlled recovery and recycling of Pd nanoparticles with application in the semihydrogenation of phenylacetylene

“Smart” nanoparticle (NP) catalysts modulated by external stimuli are an effective way of separating and recycling soluble transition metals. Light, as an external stimulus, has the advantages of cleanliness, rapid response, and non-invasiveness, which has led to the widespread interest in light stimulation response-modulated “smart” NP catalysts. However, to date, the separation and recovery of Pd NP catalysts by light stimulation-response remains challenging. Herein, we developed a Pd NP catalyst stabilized by lipoate-terminated nitrospiropyran L with a light stimulus-response function. Under dark conditions/UV switching stimulation, the L-Pd NPs exhibit reversible precipitation/dispersion characteristics in the tetrahydrofuran (THF)/methanol system, which can be used for the separation and recovery of the Pd NP catalyst under light stimulation. With semihydrogenation of phenylacetylene as a model reaction, the L- Pd NP catalyst can realize the effective reaction and separation of the catalyst by the light-regulated stimulation method. The catalyst was used four consecutive times, and the conversion of phenylacetylene and the selectivity of the product styrene were still more than 90%. This light-controlled “smart” Pd NPs method provides a new strategy for the recovery and recycling of soluble Pd NP catalysts.