Lactic acid (LA) has been produced with cascade reactions under non-noble metal and base-free conditions. In this work, amino acid-functionalized polyoxometalates (POMs) Ly_xH_3−xPMo₁₂O₄₀ (abbreviated as Ly_xH_3−xPMo, x = 1–3, Ly = C₆H₁₅O₂N₂, lysine) with triple active sites were fabricated, which presented a 87% LA yield at 96% glycerol conversion under mild reaction conditions attributed to the combination of basic sites, Brønsted acidic sites, suitable redox ability, and special microenvironments. The mechanism study showed that with Ly_xH_3−xPMo, glycerol was oxidized first to glyceraldehyde (GCA) and dihydroxyacetone (DHA) by the redox sites; then, the existence of basic sites led to the dehydration of DHA and GCA to pyruvaldehyde (PRA) and finally, the Brønsted acid sites catalyzed the hydration of PRA to LA. Meanwhile, the activation energies for different POMs were calculated using Arrhenius plots to confirm the effect of Ly₂H₁PMo for its highest efficiency. These hybrids acted as heterogeneous catalysts with long duration and high stability.

中文翻译：

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三功能多金属氧酸盐杂化物的制备，用于甘油向乳酸的级联转化

乳酸（LA）是在非贵金属和无碱条件下通过级联反应生产的。在这项工作中，氨基酸官能化的多金属氧酸盐（POM）Ly _x H _{3− x} PMo ₁₂ O ₄₀（缩写为Ly _x H _{3− x} PMo，x = 1-3，Ly = C ₆ H ₁₅ O ₂ N ₂，具有三个活性位点的赖氨酸被制成，在温和的反应条件下，归因于碱性位点，布朗斯台德酸性位点，合适的氧化还原能力和特殊的微环境的组合，在96％的甘油转化率下，LA的收率为87％。机理研究表明，在Ly _x H _{3− x} PMo中，甘油首先被氧化还原位点氧化为甘油醛（GCA）和二羟基丙酮（DHA）。然后，碱性位点的存在导致DHA和GCA脱水成丙酮醛（PRA），最后，布朗斯台德酸位点催化了PRA的水合成LA。同时，使用Arrhenius图计算了不同POM的活化能，以证实Ly ₂ H ₁的作用。PMo具有最高的效率。这些杂化物充当具有长持续时间和高稳定性的非均相催化剂。