All-Carbon-Linked Continuous Three-Dimensional Porous Aromatic Framework Films with Nanometer-Precise Controllable Thickness

Abstract

Inherently porous materials that are chemically and structurally robust are challenging to construct. Conventionally, dynamic chemistry is thought to be needed for the formation of uniform porous organic frameworks, but dynamic bonds can limit the stability of these materials. For this reason, all-carbon-linked frameworks are expected to exhibit higher stability performance than more traditional porous frameworks. However, the limited reversibility of carbon−carbon bondforming reactions has restricted the exploration of these materials. In particular, the challenges associated with producing uniform thin films of all-carbon-linked frameworks has inhibited the study of these materials in applications where well-defined films are required. Here, we synthesize continuous and homogeneous films of two different all-carbon-linked three-dimensional porous aromatic frameworks with nanometer-precision thickness (PAF-1 and BCMP-2). This was accomplished by kinetically promoting surface reactivity while suppressing homogeneous nucleation. Through connection of the PAF film to a gold substrate via a self-assembled monolayer and use of flow conditions to continually introduce monomers, smooth and continuous PAF films can be grown with controlled thickness. This strategy allows traditional transition metal mediated carbon−carbon cross-coupling reactions to form porous, organic thin films. We expect that the chemical principles uncovered in this study will enable the synthesis of a variety of chemically and structurally diverse carbon− carbon-linked frameworks as high-quality films, which are inaccessible by conventional methods.

The Prospect of Dimensionality in Porous Semiconductors

“…[48] Also by utilizinga monomer bearing as p 3 -core, Bçrjesson et al developed ac ontinuous flow method based on non-reversible coupling chemistry to prepare smooth continuous films 3D POPs. [49] In an attemptt oo vercomet he necessity of sp 3 carbons and coupling chemistry in all-organic 3D semiconductors, Coskune tal. recently demonstrated the preparation of epoxide-bearing 3D POPs via the Diels-Alderc ycloaddition polymerization, which was subsequently aromatized to form af irst example of af ully sp 2 -hybridized 3D graphitic porous polymer.…”

2D framework materials for energy applications

“…This includes the classes of 2D ordered polymers (2DPs), 10 2D covalent-organic frameworks (2D COFs) 11 and 2D metal–organic frameworks (2D MOFs), 12 while excluding classical polymers and similar materials ( i.e. 2D conjugated microporous polymers, 13 porous aromatic frameworks 14 ) that do not possess mentioned crystalline order and narrow pore-size distribution. Further we also exclude non-porous coordination polymers.…”

Have Covalent Organic Framework Films Revealed Their Full Potential?

“…Aside from adjusting the (co)monomer concentrations poured over the substrate, reaction temperature and residence time in the reactor can be key factors to control film properties. Notwithstanding the amorphous nature of the final material, a similar method was applied to form PAF films over prefunctionalized substrates [57], and the findings showed that flow chemistry helped to improve film quality with respect to the previously published bulk method [58].…”