Electron spin-polarization and spin lattices in the boron- and nitrogen-doped organic framework COF-5.

Covalent organic frameworks (COFs) hold great promise in several applications, such as sieves, catalytic supports and gas storage because of their unique structures and electronic properties. However, most of these metal-free COFs are nonmagnetic and cannot be directly used in spintronics. Here, based on first-principles calculations, we predict that substitutional doping of COF-5 with nitrogen and boron atoms can modify the electronic structures, inducing stable electron spin-polarization in the framework. The preferability of the different doping sites is checked. The electronic structures of the doped COF-5 are dependent on the doping sites and doping atoms, which offer high degrees of freedom to tune the electronic properties. Kagome lattices of S = 1/2 spins can be achieved in the COF-5, suggesting a promising candidate for spin-liquid materials.