Rare-earth metal-organic frameworks as advanced catalytic platforms for organic synthesis

Metal-organic frameworks (MOFs) have emerged as a new class of crystalline porous hybrid functional materials. The exceptional features of MOFs include their ultrahigh porosity, confined pore structures, configurations of active sites obtained by either the originally designed synthesis or post-synthetic modification, and tailorable chemical structures, all of which make them suitable candidates for many applications including gas storage, separation, catalysis, sensing, and many more. The advantages of MOFs for application to catalysis lie in features such as (1) their high internal surface area, which provides space for reactions; (2) catalytic activity toward organic reactions stemming from both metal and organic active functionalities; (3) selectivity originating from the well-defined pore environment; and (4) architectural and chemical stability endowed by the robust linkages made up of organic units and metal-based clusters, which enables recycling them as catalysts. Rare-earth metal-organic frameworks (RE-MOFs) are a subclass of MOFs that encompass the unique features of MOF chemistry but are notable for their intriguing architectural structures caused by the diverse coordination numbers of their metal clusters, thus distinguishing them from other MOFs for the purposes of catalysis. This review presents recent advances in using heterogeneous catalysts derived from RE-MOFs for various organic transformations. Key features of RE-MOFs are discussed including structural aspects, the nature of the active sites, and their relationships with the catalytic performance of the targeted MOFs. Special emphasis is placed on the effects of the metal oxidation state, site proximity, and ligand functionalization on catalytic performance and selectivity. We further include our perspectives, including several open questions that must be studied to help understand the fundamental chemistry of heterogeneous catalysis using RE-MOFs. (C) 2020 Elsevier B.V. All rights reserved.