Stacking

Materials science

Dihedral angle

Planar

Computer graphics (images)

Molecule

Computer science

Biphenyl

Stereochemistry

Nanotechnology

Organic chemistry

Mathematics

Tetrahedron

Combinatorics

Crystallography

Chemistry

Covalent bond

Topology (electrical circuits)

Steric effects

Hydrogen bond

Journal of the American Chemical Society

Rational construction of covalent organic frameworks (COFs) with novel structures still remains a challenge. Herein, we report the designed synthesis of two COFs, 2D-BPTA-COF and 3D-BMTA-COF, starting from biphenyl-based precursors but with different groups at the ortho positions. Both COFs exhibited high crystallinity and large surface area, and interestingly, 2D-BPTA-COF crystallizes into 2D sheets with AB stacking mode while 3D-BMTA-COF adopts a 7-fold interpenetrated structure with pts topology. This structural difference could be ascribed to the introduction of methyl groups in the building blocks, as the dihedral angle of biphenyl rings in 2D-BPTA-COF is ∼0° while in 3D-BMTA-COF it is ∼60°. Therefore, it is possible to synthesize COFs with different structures by twisting building blocks from planar to tetrahedral with steric hindrance. We believe this result represents a general and straightforward way to expand the diversity of tetrahedral nodes for constructing 3D COFs in the future, and moreover, a new tetrahedral node for constructing 3D COFs is now available.

Twist Building Blocks from Planar to Tetrahedral for the Synthesis of Covalent Organic Frameworks