Recent progress in mixed rare earth metal-organic frameworks: From synthesis to application

The synergistic effects of mixed-metal MOFs provide a promising platform to overcome the limitations of traditional monometallic MOFs and achieve superior performance, which are still in their infancy. Mixed-rare earth-based metal-organic frameworks (MRE MOFs) have emerged as a new class of mixed-metal MOFs and attracted significant attention due to the high and variable coordination numbers of rare-earth metal clusters, intriguing architectural structure, and distinguishing functional properties. Despite plenty of factors influencing the preparation of MRE MOFs, it is also a challenge to precisely characterize the states of mixed metals. Particularly, the MRE MOFs with multi-valent rare earth metal nodes are more sophisticated than mixed transition metal MOFs. Multi-scale computational calculation serves as a tool for in-depth interpretation and analysis of the MRE MOFs at the electronic level. In almost every case, several experimental techniques need to be wisely chosen to unambiguously characterize mixed-metal MOFs. In this review, we summarize the recent and important progress in the preparation method, characterization techniques of MRE MOFs prepared by mixing transition and rare-earth metals or mixing multi-rare-earth metals, and their applications in catalysis, adsorption decontamination and luminescence. Special emphasis is placed on the effects of different metals on their structure and properties. Finally, we also present a short conclusion and future research directions for MRE MOFs.