Chemically Gradient Hydrogen-Bonded Organic Framework Crystal Film

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Nanotechnology

Background:

• Hydrogen-bonded organic frameworks (HOFs) are ordered supramolecular solids with limited exploration as self-standing films.
• Fabricating centimeter-scale HOF films is challenging due to crystal inflexibility and limited interactions, restricting 2D macrostructure studies to external supports.

Purpose of the Study:

• To introduce a novel chemical gradient strategy for fabricating self-standing HOF films.
• To investigate the impact of bonding engineering on HOF film properties, specifically proton conductivity.

Main Methods:

• A chemical gradient strategy was employed to deposit HOF crystals onto an in situ-formed covalent organic polymer film.
• The fabricated film (Tam-Bdca-CGHOF) exhibited a versatile chemical bonding profile from covalent to hydrogen-bonded networks along its thickness.

Main Results:

• The kinetic-controlled Tam-Bdca-CGHOF film demonstrated enhanced proton conductivity (8.3×10⁻⁵ S cm⁻¹) compared to its rapid kinetic counterpart, Tam-Bdca-COP (2.1×10⁻⁵ S cm⁻¹).
• The study highlights the advantage of bonding-engineering within the same system for improved material performance.

Conclusions:

• The novel chemical gradient strategy enables the fabrication of centimeter-scale, self-standing HOF films.
• Bonding-engineering in HOFs is a promising approach for enhancing functional properties like proton conductivity.