Nanosize pores can turn semimetallic graphene into a semiconductor and, from being impermeable, into the most efficient molecular-sieve membrane. However, scaling the pores down to the nanometer, while fulfilling the tight structural constraints imposed by applications, represents an enormous challenge for present top-down strategies. Here we report a bottom-up method to synthesize nanoporous graphene comprising an ordered array of pores separated by ribbons, which can be tuned down to the 1-nanometer range. The size, density, morphology, and chemical composition of the pores are defined with atomic precision by the design of the molecular precursors. Our electronic characterization further reveals a highly anisotropic electronic structure, where orthogonal one-dimensional electronic bands with an energy gap of ∼1 electron volt coexist with confined pore states, making the nanoporous graphene a highly versatile semiconductor for simultaneous sieving and electrical sensing of molecular species.

The molecule–substrate interaction plays a key role in charge injection organic-based devices. Charge transfer at molecule–metal interfaces strongly affects the overall physical and magnetic properties of the system, and ultimately the device performance. Here, we report theoretical and experimental evidence of a pronounced charge transfer involving nickel tetraphenyl porphyrin molecules adsorbed on Cu(100). The exceptional charge transfer leads to filling of the higher unoccupied orbitals up to LUMO+3. As a consequence of this strong interaction with the substrate, the porphyrin’s macrocycle sits very close to the surface, forcing the phenyl ligands to bend upwards. Due to this adsorption configuration, scanning tunneling microscopy cannot reliably probe the states related to the macrocycle. We demonstrate that photoemission tomography can instead access the Ni-TPP macrocycle electronic states and determine the reordering and filling of the LUMOs upon adsorption, thereby confirming the remarkable charge transfer predicted by density functional theory calculations.

Interaction with the substrate strongly affects the electronic/chemical properties of supported graphene. So far, graphene deposited by chemical vapor deposition (CVD) on catalytic single crystal transition metal surfaces -mostly 3-fold close-packed -has mainly been studied. Herein, we investigated CVD graphene on a polycrystalline nickel (Ni) substrate, focusing in particular on (100) micrograins and comparing the observed behavior with that on single crystal Ni(100) substrate. The symmetry-mismatch leads to moiré superstructures with stripe-like or rhombic-network morphology, which were characterized by atomically-resolved scanning tunneling microscopy (STM). Density functional theory (DFT) simulations shed light on spatial corrugation and interfacial interactions: depending on the misorientation angle, graphene is either alternately physi-and chemisorbed or uniformly chemisorbed, the interaction being modulated by the (sub)nanometer-sized moiré superstructures. Ni(100) micrograins appear to be a promising substrate to finely tailor the electronic properties of graphene at the nanoscale, with relevant perspective applications in electronics and catalysis. of the graphene lattice, which leads to alternate strongly-and weakly-interacting regions across the moiré supercells [13][14][15][16][17][18]. In contrast, the weak coupling between graphene and other transition metals (such as copper (Cu), iridium (Ir) and platinum) results in large interfacial spacing out of the range of chemisorption, smaller spatial corrugation of moirés with respect to strongly-coupled systems, and limited rotational alignment between graphene and the substrate [19][20][21][22][23]. From an electronic point of view, the band structures for chemisorbed graphene (such as that on Ni(111) or Ru(0001)) are fragmented or disrupted due to the hybridization of the graphene π state and the metal d orbital, while physisorbed graphene typically shows Dirac cones similar to its pristine form [24][25][26]. Therefore, the magnitude of energy gap opening, interface charge polycrystalline Ni foils are also explored, thereby bridging the material gap from single crystal to realistic, non-ideal surfaces for STM measurements. Indeed, the (100) facet is one of the most common orientations present in polycrystalline Ni foils or thin films, as reported in literature [29,37] and further corroborated in this work. In addition, nickel is among the class of most-utilized metallic catalysts for CVD growth of graphene [5][6]38]. This work is therefore of potential interest for the scalable production and applications of graphene. Our results indicate that graphene structures observed on both single-and poly-crystalline substrates are highly nanometer scale. Generally, graphene moiré originates from lattice mismatch and/or angular misorientation in two isosymmetric overlapping periodic lattices; herein the situation is further complicated by the symmetry mismatch of the two interface lattices. In figures 2(a-c), from left to right, we show three STM images with incr...

We report the on-surface synthesis of graphene nanoribbon superlattice arrays directed by the herringbone reconstruction of the Au(111) surface. The uniaxial anisotropy of the zigzag pattern of the reconstruction defines a one dimensional grid for directing the Ullmann polymerization and inducing periodic arrays of parallel ultra-long nanoribbons (>100 nm), where the periodicity is varied with coverage at discrete values following a hierarchical templating behavior.