Exquisite control of electronic and spintronic properties on highly porous 2D covalent organic frameworks (COFs)

Two-dimensional covalent organic frameworks (2D COFs) are layered crystalline organic porous materials. Their high surface area and excellent synthesis modularity make them attractive candidates for electronic, optoelectronic, and catalytic applications. However, their implementation is limited due to relatively poor π-delocalization. Practical applications require controlling and tuning their electronic structure. This work uses hybrid density functional theory to computationally explore a freestanding bilayer 2D COF architecture. We systematically study the intercalation of first-row transition metals in the bilayer as a method to enhance and fine-tune its electronic properties, we also explore all magnetic configurations compatible with the system's symmetry. This resulted in a total of one pristine bilayer, 64 intercalated bilayers, and one trilayer 2D COF. We find that the concentration and position of transition metals drastically change the 2D COFs' electronic and magnetic properties. Based on their spin-polarized electronic structure, we highlight potential applications in photocatalysis and optoelectronics. Finally, we discover that several of these compounds present spintronic features, including half-metal, half-semiconductor, and bipolar magnetic semiconductor behavior, which have not been widely studied for 2D COFs in the past and are difficult to find in the same family of materials.