Scanning tunnelling microscopy (STM) images of a two-dimensional metal-organic framework.
Covalent organic frameworks (COFs) are materials formed by the linkage of organic building blocks to create periodic structures. This enables the construction of tailor-made systems for applications in (photo-)catalysis and optoelectronics. The formation of extended COFs is achieved through on-surface synthesis, which makes use of atomically flat surfaces as templates to confine polymerization reactions in two dimensions. The COFs are characterized at the atomic scale by high-resolution scanning tunneling microscopy (STM) and near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), shedding light onto the reaction pathways leading to the growth of COFs.