Chemoselective Hydrogenation of Crotonaldehyde Catalyzed by an Au@ZIF-8 Composite

Au nanoparticles of size 2.2 nm were encapsulated in a zeolitic imidazolate framework ZIF-8 framework (Au@ZIF-8). The composite was used as a catalyst for the selective hydrogenation of crotonaldehyde to crotyl alcohol with 90-95 % selectivity. Hydrogenation of 1-hexene yielded n-hexane in approximately the same conversion as crotonaldehyde, whereas cis-cyclohexene did not detectably react. To account for the confined environment of the ZIF, we supported Au nanoparticles on the outside of ZIF-8 (Au/ZIF-8). Using Au/ZIF-8 as a catalyst, 1-hexene and cis-cyclohexene were hydrogenated in low conversion whereas crotonaldehyde would only react at higher pressures in 70 % selectivity towards crotyl alcohol. Post-experiment TEM analysis of Au/ZIF-8 showed significant sintering whereas the median particle size of Au@ZIF-8 remained almost unchanged. Au@ZIF-8 was recycled as a catalyst for the hydrogenation of crotonaldehyde three times without significant loss of activity or selectivity.