Covalent organic frameworks (COFs) have attracted significant attention over the last decade due to useful characteristics such as robust covalent coupling, diverse geometries, and tunable functionality. Exploration of single-layer two-dimensional (2D) COFs is important for achieving a better understanding of their chemical and physical properties, as well as for paving the way toward integrating COFs into future electronic devices. Here we present the synthesis and electronic structure characterization of a porphyrin-based single-layer 2D COF having a square lattice with a core-linker configuration. Precursor molecules 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMA) and 5,10,15,20-tetrakis (4-aminophenyl) porphyrin (TAPP) were deposited onto a Au(111) surface in ultra-high vacuum (UHV) and annealed to form a 2D COF through a Schiff-base condensation reaction. Scanning tunneling microscopy (STM) and spectroscopy (STS) were used to study the chemical and electronic structure of the resulting 2D COF. We find that this COF has a band gap of 1.98 eV ± 0.04 eV and that both the conduction band minimum and valence band maximum states are primarily localized to the porphyrin core.

Probing the local electronic structure of a porphyrin-based single-layer covalent organic framework using STS

253rd National Meeting (2017)

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