This tutorial review addresses the formation and properties of surface-confined molecular networks as revealed with scanning probe microscopy tools, especially scanning tunneling microscopy. It could be of interest to all interested in surface nano-engineering, and supramolecular chemistry on surfaces. More specifically, this review highlights recent developments in the design of regular nanoporous networks, with a pore diameter ranging from 1 nm to more than 10 nm. The principles leading to their formation are treated in detail and the various functionalities of these porous networks are demonstrated.

Since the serendipitous event that led to the first synthesis of a molecule by the hands of Man in 1826, the creation of molecular matter depended for 150 years on linking together molecules from other molecular building blocks with the help of strong covalent bonds. The advent of supramolecular chemistry in the last decades of the 20th century has provided chemists with a wealth of new possibilities to synthesize molecular structures and materials that are held together by relatively weak, non-covalent interactions, such as hydrogen bonding, π–π stacking, electrostatic and van der Waals interactions. Using nature as a source of inspiration, the creation of even more complex supramolecular architectures has recently become possible by applying the concept of hierarchical self-assembly, i.e. the non-covalent organization of molecules and macromolecules which takes places over distinct multiple levels, in which the assembly processes gradually decrease in strength. This review will focus on some recent discoveries in the field of spontaneous hierarchical organization of synthetic amphiphiles, disk-like molecules and concave building blocks into well-defined nano-sized assemblies.

The use of bottom-up approaches to construct patterned surfaces for technological applications is appealing, but to date is applicable to only relatively small areas (∼10 square micrometers). We constructed highly periodic patterns at macroscopic length scales, in the range of square millimeters, by combining self-assembly of disk-like porphyrin dyes with physical dewetting phenomena. The patterns consisted of equidistant 5-nanometer-wide lines spaced 0.5 to 1 micrometers apart, forming single porphyrin stacks containing millions of molecules, and were formed spontaneously upon drop-casting a solution of the molecules onto a mica surface. On glass, thicker lines are formed, which can be used to align liquid crystals in large domains of square millimeter size.