A visible light/heat responsive covalent organic framework for highly efficient and switchable proton conductivity† † Electronic supplementary information (ESI) available: Materials and instrumentation methods, synthetic procedures, Nyquist plots under ideal conditions, FT-IR spectra, SEM and TEM images, BET plots, TGA analysis, PXRD patterns, XPS spectra, UV-vis spectra, stability test, water vapor sorption isotherms and proton conductivity measurement. See https://doi.org/10.1039/d2sc02100e

ABSTRACT: In recent years, covalent organic frameworks (COFs) have attracted enormous interest as a new generation of proton-exchange membranes, chemical sensors and electronic devices. However, to design high proton conductivity COFs, especially those with stimulus responsive performance remains a great challenge. Here, the first example of a light/heat switchable COF (COF-HNU9) has been synthesized by grafting a donor–acceptor Stenhouse adduct (DASA) within the channels of a β-ketoenamine-based COF. DASA groups in the nanopores of COF-HNU9 undergo a reversible open–closed photoisomerization upon visible light irradiation and are recovered by heating. Thus, COF-HNU9 exhibits not only a remarkably high proton conductivity, but also a highly effective switching performance. Under visible light irradiation at 98% RH, the proton conductivity of COF-HNU9 increases by three orders of magnitude at 25 °C and is up to 0.02 S cm−1 at 80 °C. Furthermore, the proton conductivity does not display any significant decrease even after 20 switching cycles. These results have been rationalized by a Grotthuss-type mechanism and verified by DFT calculations. The stimuli-responsive COF is conceptually confirmed by an optical control device with the light/heat switching proton conductive COF-HNU9 film, which is able to remote-control the illumination and switching off of an LED lamp without any current amplifier. A novel visible light/heat responsive 2D COF is designed and synthesized to achieve high proton conductivity (0.02 S cm−1), remarkable conductivity modulation (three orders of magnitude), and excellent recyclability (more than 20 cycles).

SUBMITTER: Chen Y 

PROVIDER: S-EPMC9132063 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature