PEG-stabilized coaxial stacking of two-dimensional covalent organic frameworks for enhanced photocatalytic hydrogen evolution

Ting Zhou,Qingliang Song,Kaito Takahashi,Changchun Wang,Hualei Zhang,Xingye Huang,Qingyuan Yang,Junjuda Unruangsri,Jia Guo,Weihua Li,Hangxun Xu,Rong Wang,Lei Wang

doi:10.1038/s41467-021-24179-5

Abstract

Two-dimensional covalent organic frameworks (2D COFs) featuring periodic frameworks, extended π-conjugation and layered stacking structures, have emerged as a promising class of materials for photocatalytic hydrogen evolution. Nevertheless, the layer-by-layer assembly in 2D COFs is not stable during the photocatalytic cycling in water, causing disordered stacking and declined activity. Here, we report an innovative strategy to stabilize the ordered arrangement of layered structures in 2D COFs for hydrogen evolution. Polyethylene glycol is filled up in the mesopore channels of a β-ketoenamine-linked COF containing benzothiadiazole moiety. This unique feature suppresses the dislocation of neighbouring layers and retains the columnar π-orbital arrays to facilitate free charge transport. The hydrogen evolution rate is therefore remarkably promoted under visible irradiation compared with that of the pristine COF. This study provides a general post-functionalization strategy for 2D COFs to enhance photocatalytic performances.

Highlights

Two-dimensional covalent organic frameworks (2D COFs) featuring periodic frameworks, extended π-conjugation and layered stacking structures, have emerged as a promising class of materials for photocatalytic hydrogen evolution
As a high-crystallinity COF enforces the planarity of the whole 2D framework and facilitates the layered π-interaction, the synthesis was thoroughly optimized by varying the reaction conditions
Pyrrolidine (Py) was used as a catalyst, instead of the aqueous acetic acid solution, for the formation of β-ketoenamine linkages

Summary

Introduction

Two-dimensional covalent organic frameworks (2D COFs) featuring periodic frameworks, extended π-conjugation and layered stacking structures, have emerged as a promising class of materials for photocatalytic hydrogen evolution. These are unfavorable for intermolecular charge transfer toward photocatalytic active sites In this context, two-dimensional covalent organic frameworks (2D COFs), which constitute a typical class of crystalline organic porous materials[5,6,7], have attracted increasing attention toward the photocatalytic hydrogen evolution[8,9]. Two-dimensional covalent organic frameworks (2D COFs), which constitute a typical class of crystalline organic porous materials[5,6,7], have attracted increasing attention toward the photocatalytic hydrogen evolution[8,9] Such 2D COFs have a delocalized π-electronic system in the framework and layered structure that is stabilized by πstacking. These inspiring studies motivate us to explore a polymer-infiltrated 2D

Methods

Results

Conclusion