Twist Building Blocks from Planar to Tetrahedral for the Synthesis of Covalent Organic Frameworks
Chao Gao1, Jian Li2,3, Sheng Yin1
1Sauvage Center for Molecular Sciences and Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, College of Chemistry and Molecular Sciences , Wuhan University , Wuhan 430072 , China.
Abstract:
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.
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