Oil–Water–Oil Triphase Synthesis of Ionic Covalent Organic Framework Nanosheets

Abstract

Ionic covalent organic framework nanosheets (iCOFNs) with long-range ordered and mono-dispersed ionic groups hold great potential in many advanced applications. Considering the inherent drawbacks of oil-water biphase method, herein, we explore an oil-water-oil triphase method based on phase engineering strategy for the bottom-up synthesis of iCOFNs.The middle water phase serves as aconfined reaction region, and the two oil phases are reservoirs for storing and supplying monomers to the water phase.Al arge aqueous space and lowm onomer concentration lead to the anisotropic gradual growth of iCOFNs into few-layer thickness,l arge lateral size, and high crystallinity.N otably,t he resulting three cationic and anionic iCOFNs exhibit ultra-high aspect ratios of up to 20,000. We further demonstrate their application potential by processing into ultrathin defect-free COF membranes for efficient biogas separation. Our triphase method may offer an alternative platform technology for the synthesis and innovative applications of iCOFNs.

Ultrathin Covalent Organic Framework Anchored on Graphene for Enhanced Organic Pollutant Removal

“…Thus far, efforts have been made to synthesize ultrathin COF nanosheets through various methods, including the top‐down exfoliation strategy from bulk counterparts, which takes advantage of ball milling, [23] solvent‐assisted sonication, [24] or chemical exfoliation, [25] and bottom‐up synthesis strategies, such as interfacial synthesis [26–28] and on‐surface synthesis [29] . However, neither strategy is suitable for large‐scale preparation of the target products because the former usually leads to uncontrollable thickness with very low yields, while the latter requires very dilute concentration of precursors and long reaction time (e.g., a few days, even one month).…”