On-Surface Self-Assembly of a C -Symmetric π-Conjugated Molecule Family Studied by STM: Two-Dimensional Nanoporous Frameworks.

The on-surface self-assembled behavior of four C -symmetric π-conjugated planar molecules (Tp, T12, T18, and Ex) has been investigated. These molecules are excellent building blocks for the construction of noncovalent organic frameworks in the bulk phase. Their hydrogen-bonded 2D on-surface self-assemblies are observed under STM at the solid/liquid interface; these structures are very different to those in the bulk crystal. Upon combining the results of STM measurements and DFT calculations, the formation mechanism of different assemblies is revealed; in particular, the critical role of hydrogen bonding in the assemblies. This research provides us with not only a deep insight into the self-assembled behavior of these novel functional molecules, but also a convenient approach toward the construction of 2D multiporous networks.