Surface functionalized sorbent particles for vapor-phase mercury removal, especially in the presence of SO3 in, for example, flue gas. The sorbent surface is modified to increase the SO3 resistance of vapor-phase mercury sorbents. The mercury removal efficiency is immune to the presence of SO3, which is not the case with conventional activated carbon as well as brominated activated carbons. The sorbent is based on carbon particles with a metal oxide coating on the surface. The thin metal oxide layer acts as an amenable surface to introduce functional groups. The metal oxide coated carbon was further modified with amine molecules, to increase its resistance towards SO3 poisoning.