Abstract In solid basic catalysis field, how to achieve optimized activity and desired stability through elaborate control over basic site properties remains a challenge. In this work, taking advantage of the structure memory effect of layered double hydroxides (LDHs), rehydrated Ca4Al1-xGax-LDHs and Ca4Al1-xInx-LDHs catalysts were prepared and applied in aldol condensation reaction that isobutyraldehyde (IBD) reacts with formaldehyde (FA) to obtain hydroxypivalaldehyde (HPA). Notably, the resulting re-Ca4Al0.90Ga0.10-LDHs exhibits an extraordinarily-high catalytic activity (HPA yield: 72%), which is to our best knowledge the highest level in this reaction. The weak Bronsted basic site, 7-coordinated Ca-OH group, which serves as an active site, catalyzes the condensation process and promotes the product desorption. Studies on structure-property correlations demonstrate that Ga as a structural promoter induces a moderate expansion of the laminate lattice, which results in a significant increase in the concentration of weak basic sites in re-Ca4Al0.90Ga0.10-LDHs, accounting for its high catalytic activity. This work illuminates that geometric structure of basic active sites can be tuned via introducing catalyst additive, which leads to a largely improved performance of hydrotalcite solid basic catalysts towards aldol condensation reaction.

中文翻译：

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几何效应促进水滑石催化剂向羟醛缩合反应

摘要 在固体碱性催化领域，如何通过精细控制碱性位点特性来达到优化的活性和所需的稳定性仍然是一个挑战。本工作利用层状双氢氧化物（LDHs）的结构记忆效应，制备了再水化的Ca4Al1-xGax-LDHs和Ca4Al1-xInx-LDHs催化剂，并将其应用于异丁醛（IBD）与甲醛（FA）反应的羟醛缩合反应中。 ) 获得羟基新戊醛 (HPA)。值得注意的是，所得的 re-Ca4Al0.90Ga0.10-LDHs 表现出非常高的催化活性（HPA 产率：72%），据我们所知，这是该反应中的最高水平。弱Bronsted碱性位点，7-配位的Ca-OH基团作为活性位点，催化缩合过程并促进产物解吸。结构-性能相关性研究表明，Ga 作为结构促进剂诱导层状晶格适度膨胀，导致 re-Ca4Al0.90Ga0.10-LDHs 中弱碱性位点的浓度显着增加，占其高催化活性。这项工作表明，可以通过引入催化剂添加剂来调整碱性活性位点的几何结构，从而大大提高水滑石固体碱性催化剂对羟醛缩合反应的性能。