One-Dimensional van der Waals Porous Fibrils Assembled from Metal-Organic Polyhedra.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Supramolecular systems achieve collective functions through hierarchical assembly.
• Metal-organic polyhedra (MOPs) are functional supramolecular architectures with cavities.
• Existing MOP assemblies into 3D networks often result in brittle materials due to poor stress dissipation.

Purpose of the Study:

• To develop MOP assemblies with enhanced mechanical flexibility and permanent porosity.
• To explore the formation of one-dimensional (1D) MOP assemblies.
• To investigate strategies for improving the mechanical properties of supramolecular materials.

Main Methods:

• Synthesis of octahedral copper-based MOPs using amino acid-functionalized naphthalenediimide (NDI) linkers and copper salts.
• Spontaneous self-assembly of MOPs into supramolecular gels and subsequent conversion to aerogels.
• Characterization of aerogel structure (1D fibrillar networks) and mechanical properties (compressive strain).
• Single-crystal X-ray diffraction to determine the 1D helical chain structure of MOPs.
• Analysis of self-assembly using Hansen solubility parameters to identify driving forces for anisotropic assembly.

Main Results:

• Successful synthesis of MOPs and their self-assembly into 1D supramolecular polymeric aerogels.
• Aerogels exhibited uniform 1D fibrillar networks with intrinsic microporosity.
• The aerogel demonstrated exceptional mechanical flexibility, enduring 87% compressive strain without fracture.
• Single-crystal X-ray diffraction confirmed a 1D helical chain structure formed by face-to-face MOP interactions.
• Hansen solubility parameter analysis indicated that high polarity and low dispersion interactions promote anisotropic assembly.

Conclusions:

• One-dimensional self-assembly of MOPs yields supramolecular polymeric aerogels with combined microporosity and significant mechanical flexibility.
• Dimensional control of MOP assemblies is a viable strategy for tailoring mechanical properties of supramolecular materials.
• This approach offers a new pathway for designing robust and adaptable soft materials.