Covalent photofunctionalization and electronic repair of 2H-MoSvia nitrogen incorporation.

A route towards covalent functionalization of chemically inert 2H-MoS exploiting sulfur vacancies is explored by means of (TD)DFT and GW/BSE calculations. Functionalization via nitrogen incorporation at sulfur vacancies is shown to result in more stable covalent binding than via thiol incorporation. In this way, defective monolayer MoS is repaired and the quasiparticle band structure as well as the remarkable optical properties of pristine MoS are restored. Hence, defect-free functionalization with various molecules is possible. Our results for covalently attached azobenzene, as a prominent photo-switch, pave the way to create photoresponsive two-dimensional (2D) materials.