In the past 30 years, metal–organic frameworks (MOFs) have garnered widespread attention owing to their diverse chemical structures, and tunable properties. As a result, MOFs are of interest for a wide variety of potential applications spanning multiple scientific and engineering disciplines. MOFs have been synthesized using several elements from the periodic table, including those with metal nodes containing s-, p-, d-, and f-block elements. MOFs synthesized with rare-earth (RE) elements, which include scandium, yttrium and the series of fifteen lanthanides are an intriguing family of MOFs from the standpoint of both structure and function. While RE-MOFs can possess many of the same properties common to all MOF families (i.e., permanent porosity, tunable pore size/shape, accessible Lewis acidic sites), they can also display unique structures and properties owing to the high coordination numbers and distinct optical properties of RE-elements. In this review, we present the progress, and highlight several discoveries from research conducted on the topic of RE-MOFs. First, diverse structures of RE-MOFs are presented, divided into classes based on the composition of the RE-metal node being RE(III)-ions, RE(III)-chains, or RE(III)-clusters. Then, several potential applications of RE-MOFs are presented, highlighting examples in the areas of chemical sensing, white light emission, biological imaging, drug delivery, near infrared emission, catalysis, gas adsorption, and chemical separations.

Intricacy anchored by uranium: Metal-organic frameworks generally have one level of assembly complexity: Organic linkers join inorganic nodes in a repeating lattice. Li et al. created a structure composed of cuboctahedra, assembled from uranium cations and organic linkers, that shared triangular faces to form prisms. These structures formed cages, which in turn joined to make tetrahedra that assembled with a diamond-lattice topology. This hierarchical open structure generated a huge unit cell with more than 800 nodes and linkers, containing internal cavities with diameters of 5 and 6 nm. Science , this issue p. 624