The book attempts to make available the recent developments in polyoxometalate (POM) synthesis. The focus centralises on the functionalisation of POMs with covalently organic moiety (for instance, the use of exogenous ligands such as carboxylate or bisphosphonate). It also delves into the development of lanthanide POMs, or the formation of blackberry-like assemblies. Likewise, the properties (redox properties, magnetism, etc...), and its applications (homogeneous and heterogeneous catalysis, photocatalysis, photoelectrocatalysis and photovoltaic cell development, etc.) are also analysed. This application concerns also the catalysis of H2O oxidation, photodegradation of pollutants, and reduction of cationic metal to form original nanoparticles. The use of polyoxometalates as catalysts for biologically relevant reactions is also considered. One of the other aims of the book is to highlight some recent developments and perspectives in the domain of materials and their applications. For instance, the use of POM-organic photosensitiser hybrids can also be achieved for application in the generation of photocurrent and the development of new types of solar cells. By combining POMs with electrically active materials, a variety of applications have been explored and several examples of POM-based electronic materials are presented in this book.