The chemoselective hydrogenation of unsaturated carbonyl compounds is one of the most important and challenging chemical processes in the fine chemical synthesis field, where intermetallic compounds (IMCs) have attracted extensive interest as efficient catalysts. In this work, we demonstrate the preparation of several Ni–In IMCs (Ni3In, Ni2In, NiIn, and Ni2In3) with a tunable particle size via the utilization of layered double hydroxides (LDHs) precursors that exhibit largely enhanced catalytic activity and selectivity toward the hydrogenation of α,β-unsaturated aldehydes. H2-TPR and semi-in situ XRD measurements reveal a coreduction process in the topotactic transformation of NiIn-LDHs materials to Ni–In IMCs. The catalytic behavior toward various unsaturated carbonyl compounds (e.g., furfural, 1-phenyltanol, crotonaldehyde, and 2-hexenal) can be improved by the modulation of the Ni/In ratio and the particle size of these Ni–In IMCs. For instance, a yield of 99% for the hydrogenation of furfural to furfuryl alcohol was obtained over supported Ni2In catalyst (particle size 5.1 nm, 110 °C, 3 MP, 2 h). The XAFS characterization and DFT calculation further reveal the electron transfer and active-site isolation in Ni–In IMCs, accounting for the largely enhanced hydrogenation selectivity. The control over the activity and selectivity of Ni–In IMCs catalysts makes them promising candidates for the chemoselective hydrogenation of unsaturated carbonyl compounds.

We report a new synthetic strategy for the fabrication of several supported nickel phosphides (Ni 12 P 5 , Ni 2 P, and NiP 2 ) with particle size ranging in 5−15 nm via a two-step procedure: preparation of supported Ni particles from layered double hydroxide precursors, followed by a further reaction with certain amount of red phosphorus. The selective hydrogenation of phenylacetylene over these metal phosphides was evaluated, and the as-prepared Ni 2 P/Al 2 O 3 catalyst show a much higher selectivity to styrene (up to 88.2 %) than Ni 12 P 5 /Al 2 O 3 (48.0 %), NiP 2 /Al 2 O 3 (65.9 %) and Ni/Al 2 O 3 (0.7 %) catalysts. EXAFS and in situ IR measurements reveal that the incorporation of P increases the bond length of Ni−Ni, which imposes a key influence on the adsorption state of alkene intermediates: as the Ni−Ni bond length extends to 0.264 nm, the alkene intermediate undergoes di-π(C=C) adsorption, facilitating its desorption and the resulting enhanced selectivity. Moreover, electron transfer occurs from Ni to P, as confirmed by EXAFS, XPS and in situ CO-IR experiment, in which the positively-charged Ni reduces the desorption energy of alkene and thus improves the reaction selectivity.

Selective hydrogenation of unsaturated carbonyl compounds plays a key role in the production of fine chemicals and pharmaceutical agents. In this work, two kinds of intermetallic compounds (IMCs: CoIn3 and CoGa3) were prepared via structural topotactic transformation from layered double hydroxide (LDH) precursors, which exhibited surprisingly high catalytic activity and selectivity toward hydrogenation reaction of α,β-unsaturated aldehydes (CO vs CC). Notably, the CoGa3 catalyst shows a hydrogenation selectivity of 96% from cinnamaldehyde (CAL) to cinnamyl alcohol (COL), significantly higher than CoIn3 (80%) and monometallic Co catalyst (42%). A combination study including XANES, XPS, and CO-IR spectra verifies electron transfer from Ga (or In) to Co, leading to the formation of CoGa (or CoIn) coordination. FT-IR measurements and DFT calculation studies substantiate that the electropositive element (Ga or In) in IMCs serves as an active site and facilitates the adsorption of polarized CO, while CC adsorption on the Co site is extremely depressed, which is responsible for the markedly enhanced selectivity toward hydrogenation of CO. This work reveals the key role of functional group adsorption in determining the hydrogenation selectivity of α,β-unsaturated aldehydes, which gives an in-depth understanding on the structure–property correlation and reaction mechanism.

An intermetallic compound (Ni3Sn2) was prepared from a hydrotalcite precursor, which exhibited outstanding hydrogenation selectivity from furfural to furfuryl alcohol.