Design And Assembly Of Novel Covalently Modified Organic Frameworks Of Polyoxometalate Clusters

The framework materials constructed by the reaction of polyoxometalates with organic ligands and transition metals have been extensively studied and reported for their novel structures and properties.In the structure,the transition metal plays a bridging role,not only coordinating with the terminal oxygen atom of the polyoxometalate,but also coordinating with the organic ligand,thus forming a specific framework structure.However,most of the structures are formed incidentally,and it is difficult to reasonably design and obtain the required structure by evaluating the geometric shapes and coordination numbers of the polyoxometalate and the organic ligand.Therefore,it is of great significance and challenge to construct a specific frame structures through the design of polyoxometalate templates.In order to solve the above problems,this paper takes advantage of the advantages of Anderson-type and Lindqvist-type POMs that are easily to be covalently modified,and through the synthesis strategy of organic alkoxylation,covalently connects them with a number of triol ligands RC（CH₂OH）₃ to synthesize a series of POMs with different coordination capacities and coordination numbers,and then coordinates with transition metal Ag to form POM-based organic frameworks with different dimensions.The specific research work is as follows:（1）we have successfully prepared a series of bilaterally symmetric modified Mn-Anderson clusters using five different triol ligands by the reflux method and coordinated them with Ag ions to obtain a series of crystal structures with different dimensions.When the coordination group was in the middle,it tended to form a 0D cluster structure,while when the coordination group was at both ends,it tended to form a 1D long-chain structure.（2）By further expanding the types of POMs,we constructed a series of symmetric V₆-Lindqvist clusters with functional organic groups covalently modified,and explored their coordination behaviors with Ag ions.We obtained a conclusion similar to that in the first point,which proves the universality of the method.A deeper understanding of the coordination mechanism of Ag ions with organic modified POMs provided more references for later design and preparation of POM-based materials with expected structures.