Entanglement of Square Nets in Covalent Organic Frameworks

Fangying Jin; Ha L Nguyen; Zhiye Zhong; Xing Han; Chenhui Zhu; Xiaokun Pei; Yanhang Ma; Omar M Yaghi

doi:10.1021/jacs.1c13468

Entanglement of Square Nets in Covalent Organic Frameworks

J Am Chem Soc. 2022 Feb 2;144(4):1539-1544. doi: 10.1021/jacs.1c13468. Epub 2022 Jan 24.

Authors

Fangying Jin¹, Ha L Nguyen^{1

2}, Zhiye Zhong³, Xing Han¹, Chenhui Zhu⁴, Xiaokun Pei¹, Yanhang Ma³, 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, United Arab Emirates University, Al-Ain 15551, United Arab Emirates.
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: 35068156
DOI: 10.1021/jacs.1c13468

Abstract

Two entangled 2D square covalent organic frameworks (COFs) have been synthesized from 4,4',4″,4‴-(9,9'-spirobi[fluorene]-2,2',7,7'-tetrayl)-tetrabenzaldehhyde (SFTB) and p-phenylenediamine (PPA) and benzidine (BZD) to form COF-38, [(SFTB)(PPA)₂]_imine, and its isoreticular form COF-39, [(SFTB)(BZD)₂]_imine. We also report the single-crystal electron diffraction structure of COF-39 and find that it is composed of mutually entangled 2D square nets (sql). These COFs represent the first examples of entangled 2D COF structures, which, as we illustrate, were made possible by our strategy of using the distorted tetrahedral SFTB building unit. SFTB overcomes the propensity of 2D COFs to stack through π-π stacking and allows entanglements to form. This work significantly adds to the design principles of COFs.