Exquisite control of electronic and spintronic properties on highly porous Covalent Organic Frameworks (COFs): transition metal intercalation in bilayers

Abstract

Two-dimensional covalent organic frameworks (2D COFs) are crystalline organic porous materials stacked in a layered fashion. In general, these materials have excellent structural tunability, which can be achieved through the various tools of organic synthesis. Their layered and porous nature makes them attractive candidates for electronics, optoelectronics, and catalysis. However, their application is still limited due to relatively poor π-delocalization and practical applications require controlling and tuning their electronic structure. In this paper, using hybrid density functional theory, we computationally explore a novel 2D COF architecture, consisting of only two crystalline atomic layers made of benzene, boroxine, and triazine rings. We study the intercalation of first-row transition metals in the bilayer to enhance and fine-tune their electronic and magnetic behavior. This resulted in the development of one pristine bilayer, 63 intercalated bilayers, and one trilayer 2D COF. We found that the concentration and position of transition metals in the structure can drastically change the 2D COFs’ electronic, magnetic, and spintronic features. Based on their spin-polarized electronic properties, these transition metal-intercalated 2D COFs have potential applications as water splitting catalysts, direct semiconductors in the visible range, half metals, half semiconductors, and bipolar magnetic semiconductors.