Novel solid acid materials based on polyoxometalates

强固体酸已被广泛应用于化工和石油化工过程中作为环境友好的多相酸催化剂，燃料电池中的质子导电膜，分离和净化技术中碱性杂质的选择性吸附剂等。固体酸在这种应用中的效率主要取决于它们的酸强度和热稳定性。具有强酸位和高稳定性的有效固体酸的选择是有限的，因此在许多应用领域对这类材料的强烈需求。在有希望的初步实验之后，我们提出了一个合作计划，汇集了多相催化，材料化学和固态核磁共振方面的专家，以开发基于多金属氧酸盐的具有强酸性和高热稳定性的新型功能化材料的合成能力。典型的多金属氧酸盐的酸性形式，被称为杂多酸，是非常强的质子酸，但它们的稳定性相对较低。拟议的计划旨在通过多组分氧化体系的转化制备固体酸材料。初步实验表明，在这种体系中形成了一种高度稳定的强酸性二维杂多酸相，在催化和其他应用中具有潜在的有效性。在提出的工作中，将使用基本的混合和安装程序来制备酸性材料。这样制成的材料的结构将在不同的层次上得到彻底的表征。对结构的理解对于制定合成新材料的总体策略至关重要。我们还希望建立这些材料的结构特征与它们的酸度、催化活性和离子电导率之间的关系。材料的催化性能将通过模型反应与标准固体酸催化剂进行比较来详细研究。这些材料还将在一系列具有商业价值的酸催化反应中进行测试。与传统的固体酸（混合氧化物、沸石）和典型的杂多酸相比，由多组分氧化体系衍生的新型强固体酸具有重要的优势。与混合氧化物和沸石相比，它们具有更强的酸性。与典型的可溶性杂多酸相比，它们具有更高的热稳定性和溶出到液相的稳定性，可以有效地利用这些材料作为可再生的绿色固体酸催化剂、导电膜和极性溶剂中可重复使用的选择性吸附剂。

Strong solid acids have found various applications as environmentally benign heterogeneous acid catalysts for chemical and petrochemical processes, proton conductive membranes in fuel cells, selective adsorbents of basic impurities in separation and purification technologies, etc. The efficiency of solid acids in such applications depends primarily on their acid strength and thermal stability. The choice of effective solid acids possessing strong acid sites as well as high stability is limited, hence strong demand for such materials in many fields of application. Following promising preliminary experiments, we propose a collaborative programme bringing together experts in heterogeneous catalysis, materials chemistry and solid-state NMR to develop the capability for the synthesis of novel functionalised materials possessing strong acidity and high thermal stability based on polyoxometalates. The acidic forms of typical polyoxometalates, known as heteropoly acids, are very strong protonic acids, however their stability is relatively low. The proposed programme aims at the preparation of solid acid materials by a transformation of multicomponent oxidic systems. Preliminary experiments indicate the formation of a highly stable and strongly acidic two-dimensional heteropoly acid phase in such systems, which could potentially be effective in catalytic and other applications. In the proposed work, the fundamental blending and mounting procedures will be used to prepare the acidic materials. The structure of materials thus made will be thoroughly characterised at different levels. Structural understanding will be essential for the elaboration of the general strategy towards the synthesis of novel materials. We also wish to establish the relationship between the structural features of these materials and their acidity, catalytic activity and ionic conductivity. The catalytic performance of materials will be studied in detail using model reactions in comparison with standard solid acid catalysts. The materials will also be tested in a range of acid-catalysed reactions of commercial interest. The novel strong solid acids derived from multicomponent oxidic systems will have important advantages over the conventional solid acids (mixed oxides, zeolites) and typical heteropoly acids. They will have stronger acidity compared to mixed oxides and zeolites. As compared to the typical soluble heteropoly acids, they will have higher thermal stability and stability towards leaching into liquid phase, allowing effective use of these materials as regenerable green solid acid catalysts, conductive membranes and reusable selective adsorbents in polar solvents.