The covalent functionalization of BPN has not been studied before. Thus, the starting point is assessing possible adsorption sites suitable for functionalization (Scheme 2). A nomenclature is introduced, denoting the connected rings of the attacked carbon atoms. BPN consists of 4-, 6-and 8-rings where all rings of the same size are chemically equivalent. Hence, the adsorption structure named 6-4 accords to COC connected to the C-C-bond between the 6-and 4-ring of the network.