A Grafting Hydrogen‐bonded Organic Framework for Benchmark Selectivity of C₂H₂/CO₂ Separation under Ambient Conditions

Abstract

Reticular chemistry and pore engineering have garnered significant advancements in metal-organic frameworks and covalent organic frameworks, leveraging robust metal-coordination and covalent bonds. However, these achievements remain elusive in hydrogen-bonded organic frameworks, hindered by their inherent weakness in hydrogen bonding. Herein, we strategically manipulate the porosity of hydrogen-bonded frameworks through a grafting approach, culminating in the synthesis of two isomorphic HOFs, HOF-FJU-99 and HOF-FJU-100, with distinct pore environments. Remarkably, HOF-FJU-100, with its microporous architecture, not only showcases exceptional stability but also achieves unparalleled separation efficiency and ultrahigh selectivity for C₂H₂/CO₂ mixtures (50/50, v/v) under ambient conditions. Its IAST selectivity value of 201 stands as a benchmark, towering over all previously reported HOFs. The pore of HOF-FJU-100 boasts an electrostatic potential highly favourable for C₂H₂ adsorption, as evidenced by single crystal X-ray diffraction analysis revealing multiple hydrogen bonding interactions between C₂H₂ molecules and the framework. In situ gas-carrier powder X-ray diffraction analysis underscores the adaptability of pore structure, dynamically adjusting its orientation in response to C₂H₂, thereby enabling a highly efficient and specific separation of C₂H₂/CO₂ mixtures through specific adsorptive interactions.