Multifunctional polyoxometalates encapsulated in MIL-100(Fe): highly efficient photocatalysts for selective transformation under visible light

Abstract

H₃PMo₁₂O₄₀ molecules have been successfully encapsulated in the cavities of MIL-100(Fe) via a facile hydrothermal method (denoted as HPMo@MIL-100(Fe)). A series of characterization has corroborated the insertion of H₃PMo₁₂O₄₀ within the cavities of MIL-100(Fe). The resulting HPMo@MIL-100(Fe) nanocomposites have exhibited much higher photoactivity than the original-MIL-100(Fe) toward the photocatalytic selective oxidation of benzylic alcohols and the reduction of Cr(VI) under visible light irradiation (λ ≥ 420 nm). The higher photoactivity of HPMo@MIL-100(Fe) can be attributed to the integrative effect of enhanced light absorption intensity and more efficient separation of photogenerated electron–hole pairs. The host porous structure of MIL-100(Fe) can achieve a uniform composition with H₃PMo₁₂O₄₀, which is significantly important for producing highly reactive dispersed H₃PMo₁₂O₄₀ molecules and enhancing the photocatalytic activity of HPMo@MIL-100(Fe) nanocomposites. And the immobilized H₃PMo₁₂O₄₀ molecules are more convenient for recycling. Importantly, almost no Fe and Mo ions leach from the MIL-100(Fe) during the reaction, which verifies the photostability of the HPMo@MIL-100(Fe). In addition, possible photocatalytic redox reaction mechanisms have been investigated.