2D monolayer and bilayer pillararene-based hierarchically porous hydrogen-bonded organic frameworks with fast lithium-ion transport and accelerating sulfur redox reactions in lithium–sulfur batteries

Herein, we report the fabrication of a hierarchically cavity-porous bilayer and a hierarchically cavity-porous monolayer two-dimensional (2D) pillararene-based hydrogen-bonded organic framework, based on hydrogen bonds between the carboxyl groups of functionalized pillar[6]arene and between the carboxylate anions of functionalized pillar[6]arene and the amidine groups of tetraphenylethylene derivatives. These frameworks exhibit excellent structural crystallinity and stability, as characterized by single crystal X-ray diffraction, powder X-ray diffraction, high-resolution transmission electron microscopy, thermogravimetry, and gas adsorption studies. Atomic force microscopy confirms that the ultrathin thickness of the monolayer and bilayer pillararene-based hydrogen-bonded organic frameworks can be realized on the micrometre scale. Electrochemical impedance and cyclic voltammetry (CV) measurements confirm that these frameworks possess fast lithium ion diffusion channels, efficient polysulfide-capture ability, and accelerated sulfur redox kinetics in Li–S batteries. This work presents a novel and straightforward strategy and platform for designing 2D framework materials, porous materials, and Li–S battery materials with specific monolayer and bilayer configurations.