Constructing out-of-plane oriented two-dimensional covalent organic framework films for stretchable electronics

It is very desirable and important to construct two-dimensional covalent organic framework films with uniform thickness, ordered structure, clean surface and excellent semiconducting performance directly on substrates for applications in electronic devices, but achieving these characteristics simultaneously is challenging. Here, we report a Marangoni flow-aided interface synthesis method to fabricate out-of-plane oriented two-dimensional covalent organic framework films that meet all these requirements. The method can drive the orientation arrangement of 1,3,6,8-Tetrakis(4-aminophenyl) pyrene precursors with their molecular plane perpendicular to substrate surface. This enables them to undergo stereospecific polymerization with terephthalaldehyde, forming long-range ordered bonding and stacking in the out-of-plane oriented two-dimensional covalent organic framework film formed in situ, thereby achieving high conductivity. Employing the unique structure and the outstanding electronic, optical and mechanical properties of the out-of-plane oriented two-dimensional covalent organic framework, we demonstrate the great application potential of two-dimensional covalent organic framework for flexible, stretchable and foldable electronics.