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.

多金属氧酸盐（POM）具有出色的物理和化学特性，在催化，磁性，医学，光化学和材料科学等各个领域均显示出强大的潜力。通过通过自组装，接枝，掺杂或嵌入策略将有机功能部分引入POM系统，可以很好地保持POM和有机部分的优势，从而获得许多新特性。在所有现有的有机功能化的POM中，羧酸盐共价改性的POM（CCMP，共价接枝到POM骨架上的羧酸配体）吸引了深入的研究工作。羧酸配体不仅有助于丰富CCMP的结构多样性，而且由于有机配体和POM单元之间可能发生电子转移，因此还有助于调整CCMP的氧化还原行为和光还原活性。受到令人印象深刻的结构多样性以及在光学，磁性和材料科学领域潜在应用的鼓舞，新型CCMP配合物的设计和探索已成为POM化学领域中最引人注目的和最具挑战性的领域。在这篇综述中，我们在这里讨论了过去几十年中CCMP在合成方法，结构特征和相关应用（光致变色，光致发光和磁性等）方面的研究进展。此外，本文的最后一部分还介绍了一些个人见解，并真诚地希望继续探索未发现的CCMP。