3D Covalent Organic Frameworks Selectively Crystallized through Conformational Design

Ha L Nguyen; Cornelius Gropp; Yanhang Ma; Chenhui Zhu; Omar M Yaghi

doi:10.1021/jacs.0c11064

3D Covalent Organic Frameworks Selectively Crystallized through Conformational Design

J Am Chem Soc. 2020 Nov 13. doi: 10.1021/jacs.0c11064. Online ahead of print.

Authors

Ha L Nguyen^{1

2}, Cornelius Gropp¹, Yanhang Ma³, Chenhui Zhu⁴, Omar M Yaghi^{1

2}

Affiliations

¹ Department of Chemistry, University of California Berkeley; Kavli Energy Nanoscience Institute at UC Berkeley; and Berkeley Global Science Institute, Berkeley, California 94720, United States.
² Joint UAEU-UC Berkeley Laboratories for Materials Innovations.
³ School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
⁴ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.

PMID: 33186498
DOI: 10.1021/jacs.0c11064

Abstract

We present a strategy whereby selective formation of imine covalent organic frameworks (COFs) based on linking of triangles and squares into the fjh topology was achieved by the conformational design of the building units. 1,3,5-Trimethyl-2,4,6-tris(4-formylphenyl)benzene (TTFB, triangle) and 1,1,2,2-tetrakis(4-aminophenyl)ethene (ETTA, square) were reticulated into [(TTFB)₄(ETTA)₃]_imine, termed COF-790, which was fully characterized by spectroscopic, microscopic, and X-ray diffraction techniques. COF-790 exhibits permanent porosity and a Brunauer-Emmett-Teller (BET) surface area of 2650 m² g^-1. Key to the formation of this COF in crystalline form is the pre-designed conformation of the triangle and the square units to give dihedral angles in the range of 75-90°, without which the reaction results in the formation of amorphous product. We demonstrate the versatility of our strategy by also reporting the synthesis and characterization of two isoreticular forms of COF-790, COF-791 and COF-792, based on other square building units.