Are COFs the new MOFs?

Chemists who hadn’t heard of metal-organic frameworks (MOFs) before last October no doubt learned about them when the 2025 Nobel Prize in Chemistry went to three researchers who helped develop the high-surface-area materials. Discovered in the 1990s, MOFs are a family of porous crystalline solids composed of metal ions or clusters joined by organic linkers. By tailoring the metal and organic building blocks, researchers have made MOFs with extremely high internal surface area that can store hydrogen, capture carbon dioxide, harvest moisture from desert air, and remove contaminants from water. But the metals in MOFs—mainly transition metals like copper, zinc, and cobalt—are heavy and can be toxic, according to a recent analysis by CAS, a division of the American Chemical Society that specializes in scientific knowledge management. (C&EN is published by ACS.)Some researchers are exploring an alternative to MOFs called covalent organic frameworks (COFs). They are typically composed of two organic monomers that are systematically linked to form extended crystalline networks. Made entirely of light elements, COFs have outstanding chemical and thermal stability, the CAS analysis says.A team led by Omar M. Yaghi, a 2025 Nobel Prize winner, discovered COFs in 2005, and they’re now being developed for some of the same applications as MOFs are. For example, Yaghi’s team published a paper in 2024 about a COF that can capture CO2 from ambient air, a strategy for reducing greenhouse gases. A year earlier, his team reported on COFs that hang together like chains in a 3D network, which allows them