Moving Beyond Boron: The Emergence of New Linkage Chemistries in Covalent Organic Frameworks

Since their discovery in 2005, covalent organic frameworks (COFs) have attracted interest as potential materials for gas storage, catalysis, energy storage, and other applications because of their ability to periodically and reliably organize designed functionality into high surface area materials. Most of the first examples relied on boron-containing linkages, which suffer from hydrolytic and oxidative instability that limit their utility. In this Perspective, we describe the trend toward more robust linkages by highlighting the design, synthesis, and properties of several recent examples. The continued development of new COF chemistries, along with improved understanding of their formation and control of their final form, will provide a means to harness their molecularly precise solidstate structures for useful purposes.