Bifunctional role of oxygen vacancy in LDH supported Au nanoparticles catalyst for selective photocatalytic hydrogenation of cinnamaldehyde

The research on the strong interaction between metal and vacancy has made new progress. Herein, we report the bifunctional role of oxygen vacancies on in situ synthesis of Au nanoparticles photocatalyst and selective hydrogenation of alpha, ss-unsaturated aldehydes. Due to the memory effect of layered double hydroxide (LDH), LDH after high temperature calcination could restore its original layered structure and introduce a large number of oxygen vacancies. In the process of catalyst synthesis, Au3+ was in situ reduced to Au nanoparticle over LDH with the help of oxygen vacancies with special electronic environment. A 99 % conversion of cinnamaldehyde and 97 % selectivity for cinnamyl alcohol was obtained over Au/LDH-700 in the selective hydrogenation of cinnamaldehyde under visible light irradiation without bases addition. This high performance was attributed to the synergistic effect between the localized surface plasmon resonance (LSPR) effect of Au nanoparticles and the abundant oxygen vacancies in LDH. The Au nanoparticles absorb visible light to induce the dehydrogenation of isopropanol and provide stable hydrogen source for the hydrogenation reaction. The LDH rich in oxygen vacancies selectively adsorbs the -C--O group of cinnamaldehyde via the terminal oxygen mode to ensure the formation of highly selective cinnamyl alcohols. In addition, experimental data shows Au/LDH-700 catalyst could hydrogenate a variety of alpha, ss-unsaturated aldehydes and ketones into corresponding unsaturated alcohols with high conversion and selectivity. Our work points out a new direction for the selective hydrogenation of alpha, ss-unsaturated aldehydes to unsaturated alcohols.