Self-templated synthesis of uniform hollow spheres based on highly conjugated three-dimensional covalent organic frameworks

Yuan-Yuan Liu,Chen Liu,Tao Cheng,Huiyan Yang,Shi Wang,Wei Huang,Xiang-Chun Li,Wen-Yong Lai,Yanting Gong

doi:10.1038/s41467-020-18844-4

Abstract

Covalent organic frameworks (COFs) have served as a family of porous crystalline molecules for various promising applications. However, controllable synthesis of COFs with uniform morphology is paramount yet still remains quite challenging. Herein, we report self-templated synthesis of uniform and unique hollow spheres based on highly conjugated three-dimensional (3D) COFs with diameters of 500–700 nm. A detailed time-dependent study reveals the continuous transformation from initial nano sphere-like particles into uniform hollow spherical structures with Ostwald ripening mechanism. Particularly, the resulting 3D COF (3D-Sp-COF) is prone to transport ions more efficiently and the lithium-ion transference number (t+) of 3D-Sp-COF reaches 0.7, which even overwhelms most typical PEO-based polymer electrolytes. Inspiringly, the hollow spherical structures show enhanced capacitance performance with a specific capacitance of 251 F g−1 at 0.5 A g−1, which compares favorably with the vast majority of two-dimensional COFs and other porous electrode materials.

Highlights

Covalent organic frameworks (COFs) have served as a family of porous crystalline molecules for various promising applications
We report the controllable synthesis of 3D COFs (3D-Sp-COF) with uniform and unique hollow spherical morphology based on highly conjugated building blocks via self-templated synthetic methods
Spirobifluorene core Sp-4(Ph-NH2) was synthesized by Suzuki cross-coupling reaction (Supplementary Figs. 1–4). 3D COF (3DSp-COF) with spirobifluorene core and imine bonds was prepared by the solvothermal reaction between Sp-4(Ph-NH2) and terephthalaldehyde (Ph-2CHO) with an acetic acid catalyst at

Summary

Introduction

Covalent organic frameworks (COFs) have served as a family of porous crystalline molecules for various promising applications. We report the controllable synthesis of 3D COFs (3D-Sp-COF) with uniform and unique hollow spherical morphology based on highly conjugated building blocks via self-templated synthetic methods. Their formation mechanism of hollow spheres based on 3D COFs has been investigated by a detailed time-dependent study and the growth process has been dominated by Ostwald ripening. According to our preliminary specific capacitance studies, overwhelming high specific capacitance of 251 F g−1 has been achieved for 3D COFs by facilely modulating the morphological features

Methods

Results

Conclusion