Biasing the Hierarchy Motifs of Nanotoroids: from 1D Nanotubes to 2D Porous Networks

Hierarchical organization of self‐assembled structures into superstructures is omnipresent in Nature but has been rarely achieved in synthetic molecular assembly due to the absence of clear structural rules. We herein report on the self‐assembly of scissor‐shaped azobenzene dyads which form discrete nanotoroids that further organize into 2D porous networks. The steric demand of the peripheral aliphatic units diminishes the trend of the azobenzene dyad to constitute stackable nanotoroids in solution, thus affording isolated (unstackable) nanotoroids upon cooling. Upon drying, these nanotoroids organize at graphite surface to form well‐defined 2D porous networks. The photoirradiation with UV and visible light enabled reversible dissociation and reconstruction of nanotoroids through the efficient trans↔cis isomerization of azobenzene moieties in solution. The steric demand exerted by the peripheral side chains of the reported azobenzene dyads impedes their hierarchical self‐assembly from nanotoroids into nanotubes. In contrast, they organize into 2D porous networks on substrate upon solution processing. Photoisomerization of azobenzene moieties allows efficient dissociation/reorganization of nanotoroids in solution, demonstrating their potential as photoresponsive 2D porous nanosheets.