Inside polyMOFs: layered structures in polymer-based metal-organic frameworks

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Polymer metal-organic frameworks (polyMOFs) are hybrid materials combining polymer and metal-organic framework properties.
• Understanding their internal nanostructure is crucial for designing advanced functional materials.

Purpose of the Study:

• To investigate the internal structural features of polyMOFs composed of metal-coordinating and non-coordinating polymer blocks.
• To elucidate the self-assembly mechanisms governing the nanostructure of polyMOFs.

Main Methods:

• Transmission electron microscopy (TEM)
• Scanning electron microscopy (SEM)
• Energy-dispersive X-ray spectroscopy (EDS)
• Small-angle synchrotron X-ray scattering (SAXS)

Main Results:

• PolyMOFs display alternating lamellar structures of metal-rich crystalline regions and metal-deficient non-crystalline polymer domains.
• These lamellar structures span hundreds of nanometers and exhibit single-nanometer scale self-assembly.
• Similar structural alternation was observed across different copolymer architectures (random blocks, end-blocks) and non-coordinating polymers (poly(ethylene glycol), poly(cyclooctadiene)).

Conclusions:

• A universal self-assembly mechanism drives the formation of lamellar nanostructures in polyMOFs.
• The observed self-assembly is independent of copolymer architecture and composition.
• These findings provide fundamental insights into the structure-property relationships of polyMOFs.