▎ 摘　　要

Recently, He et al. succeeded in covalently linking porphines to graphene edges on a Ag(111) substrate by dehydrogenative coupling [Nat. Chem. 9 (1) (2017) 33-38], thus created a new hybrid material with tunable functionalities. Motivated by this work, we further investigate the electron transport properties of three porphine/graphene coupling motifs observed by scanning-probe technology with submolecular resolution in the experiment. By using density-functional theory combined with the Keldysh nonequilibrium Green's technique, we find many interesting electron transport phenomena in these new hybrid structures. Conductivity enhancement can be observed when porphines are covalently bound to the edges of specific armchair graphene nanoribbon (AGNR) and symmetric zigzag GNR (ZGNR). However, the origin of conductivity enhancement in the AGNR related hybrid system is completely different from that in the ZGNR related system. Moreover, negative differential resistance (NDR) behaviors can be found in ZGNR related coupling configurations. In particular, two different NDR mechanisms are found in these hybrid systems. (C) 2017 Elsevier Ltd. All rights reserved.