Efficient Synthesis of phenylacetaldehyde via interfacial catalysis by surface-active hybrid polyoxometalates

The catalytic production of phenylacetaldehyde (PhAA) from styrene using oxygen (O 2 ) as the oxidant offers advantages such as readily available feedstocks, a concise reaction route, and environmental friendliness. However, the PhAA yield of this multiphase system is generally less than 15 % due to the interfacial limitations between O 2 , styrene, and catalyst. To address this challenge, Keggin-type polyoxometalates (POMs) of the form [XW 11 O 39 ] n- (X = B, P, Si; n = 7, 8, 9) were modified with octyl trimethoxysilane (OTMS) to prepare hybrid POMs possessing both surface activity and catalytic potency. In the [Bmim][BF 4 ] ionic liquid, these hybrid POMs effectively reduce surface tension (44.7 mN/m to 31–34 mN/m) and exhibit critical aggregation behavior similar to conventional surfactants. Within the reaction system using [Bmim][BF 4 ] as a co-solvent and O 2 as the oxidant, the hybrid [SiW 11 O 39 ] achieves 76.9 % styrene conversion and ∼54 % PhAA yield after 8 h at 105 ℃. The surface activity of hybrid POM and the sub-nanometer scale effect of POM head groups promote the effective contact of O 2 , styrene, and catalyst at the phase interface. Based on the two-step reaction mechanism of epoxidation and isomerization, an efficient preparation of PhAA from styrene using O 2 as the oxidant was achieved.