Hydrogenation Chemoselective Hydrogenation of Cinnamaldehyde on Iron-Oxide Modified Pt/MoO 3y Catalysts Yijin Shu, Ting Chen, Hang Cheong Chan, Lifang Xie, and Qingsheng Gao* [a] Abstract: Hydrogenation of a,b-unsaturated aldehydes to unsaturated alcohols suffers a huge challenge in chemose- lectivity. Herein, surface decoration by FeO x is introduced to remarkably improve the selectivity of cinnamyl alcohol (COL) in cinnamaldehyde (CAL) hydrogenation on Pt/MoO 3y . The enhanced acidity on Pt–FeO x interfaces is beneficial for the chemisorption and activation of C =O bonds, promoting se- lective hydrogenation. The optimal catalysts with defined FeO x decoration afford efficient and chemoselective CAL hy- drogenation (91.3 % selectivity) under mild conditions (P H2 = 1 MPa, T = 30 8C). Moreover, such innovation is further ex- tended to develop other efficient metal (Ir, Rh and Pd) cata- lysts, identifying a universal promotion to Pt-group metals. This work is anticipated to inspire the rational design of high-performance catalysts via effective surface/interface en- gineering. Introduction Chemoselective hydrogenation of a,b-unsaturated aldehydes produces unsaturated alcohols that are important and valuable intermediates for manufacturing flavor, fragrance, pharmaceuti- cal compounds, etc. [1, 2] The hydrogenation is commercially pro- ceeded by metal hydrides (e.g., NaBH 4 , AlLiH 4 , etc.), [3] unfortu- nately causing serious pollution to environment. Catalytic sys- tems that use renewable and green reagents, for example, H 2 , are promising alternatives. [4, 5] However, the hydrogenation of C =C moiety is thermodynamically favoured in comparison with C =O, resulting in undesired aldehydes or saturated alco- hols. [1, 6–8] In view of metal-based catalysts, group VIII metals (e.g., Pt, [9, 10] Pd, [11, 12] Ir, [13–15] etc.) with a satisfactory activity seri- ously suffer from low selectivity because of the easy C =C hy- drogenation, while group IB metals (e.g., Ag [16] and Au [17, 18] ) show chemoselectivity but poor activity. Typically, strong metal-support interactions are introduced to vary the chemical states (e.g., size, atom arrangement, charge distribution, etc.) of metals and consequently the chemisorption configuration of substrates, leading to the improved catalytic activity and se- lectivity. [19–23] Thereby, the engineered interfaces between metals and supports are the key issue for exploring efficient catalysts. As reducible supports, MoO 3 delivers strong interactions with loading metals when it is hydrogen doped during prepa- ration or catalysis. [24–26] Previous experimental and theoretical investigations have identified the electronic interactions associ- ated with metallic band states near the Fermi level in partially reduced MoO 3 (MoO 3y ), [27, 28] which contributes to the im- proved activity on size-reduced or charge-redistributed metal (e.g., Pt and Ir) nanodomains. [25, 29, 30] However, the selective hy- drogenation remains as a great challenge even when catalytic turnover is highly improved, requiring further optimization on metal-support interfaces. Typically, the surface acidity of cata- lysts makes influences on the adsorption configuration of sub- strates. [31–33] For example, Lewis and Brçnsted acidic sites on metal oxides deliver strong electronic interactions with C =O bonds via M···O =C or MOH···O =C, resulting in effective activa- tion toward selective C =O hydrogenation. [34, 35] In this regard, the surface acidity (e.g., amount and strength) on metal/ MoO 3y is desired to improve via surface modification. [4, 36–39] Herein, we at first inquire the surface modification by Group VIII metal (Fe, Co and Ni) oxides for the selective hydrogena- tion of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) on Pt/ MoO 3y . The Pt/MoO 3y has demonstrated its high activity but poor selectivity for hydrogenation in our previous work. [30] Visi- bly, the COL selectivity is dependent on the acidity of Group VIII metal oxides, reaching the best after FeO x decoration due to the effective activation of C =O bonds on strong acidic sites. The FeO x modification onto Pt is further engineered to accom- plish the efficient CAL hydrogenation to COL (sel.: 91.3 %) at a mild condition (30 8C and 1 MPa H 2 ), which identifies the Pt- FeO x interfaces as the main active-sites. Moreover, the promo- tion by FeO x modification is extended to design other Pt- group metals, e.g., Ir, Rh and Pd, accomplishing the consistent enhancement in chemoselective hydrogenation. [a] Y. Shu, T. Chen, H.C. Chan, L. Xie, Prof. Dr. Q. Gao Department of Chemistry College of Chemistry and Materials Science Jinan University No. 601 Huangpu Avenue West, 510632 Guangzhou (P. R. China) E-mail : tqsgao@jnu.edu.cn Supporting information and the ORCID identification number(s) for the au- thor(s) of this article can be found under: https://doi.org/10.1002/asia.201801281. Chem. Asian J. 2018, 00,0–0  2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 && These are not the final page numbers! ÞÞ Full Paper DOI: 10.1002/asia.201801281