Carboxylate covalently modified polyoxometalates: From synthesis, structural diversity to applications

Abstract

Polyoxometalates (POMs) have demonstrated strong potential in various fields, such as catalysis, magnetism, medicine, photochemistry and materials science, for their remarkable physical and chemical properties. Through the introduction of organic functional moieties to the POM systems via self-assembly, grafting, doping or intercalation strategies, advantages from both the POMs and organic moieties are well maintained, resulting in many new properties. Among all the existing organo-functionalized POMs, carboxylate covalently modified POMs (CCMPs, carboxylic acid ligands covalently grafted to the POM skeletons) attract intensive research efforts. The carboxylic acid ligands not only help to enrich the structural diversities of the CCMPs, but also facilitate the tuning of redox behaviors and photoreduction activities of the CCMPs because of the possible electron transfer between the organic ligands and the POM units. Encouraged by the impressive structural diversities and potential applications in optics, magnetism and materials science, the design and exploration of new CCMP complexes have become some of the most compelling and challenging areas in POM chemistry. In this review, we herein discuss the research progress achieved for CCMPs in the past decades in the areas of synthesis methodologies, structural features and relevant applications (photochromism, photoluminescence and magnetism, etc.). In addition, some personal insights are also presented in the last section of the paper with sincere wishes for continuous exploration of the undiscovered world of CCMPs.