Enriching and Quantifying Porous Single Layer 2D Polymers by Exfoliation of Chemically Modified van der Waals Crystals

Abstract

2D polymer sheets with six positively charged pyrylium groups at each pore edge in a stacked single crystal can be transformed into a 2D polymer with six pyridines per pore by exposure to gaseous ammonia. This reaction furnishes still a crystalline material with tunable protonation degree at regular nano‐sized pores promising as separation membrane. The exfoliation is compared for both 2D polymers with the latter being superior. Its liquid phase exfoliation yields nanosheet dispersions, which can be size‐selected using centrifugation cascades. Monolayer contents of ≈30 % are achieved with ≈130 nm sized sheets in mg quantities, corresponding to tens of trillions of monolayers. Quantification of nanosheet sizes, layer number and mass shows that this exfoliation is comparable to graphite. Thus, we expect that recent advances in exfoliation of graphite or inorganic crystals (e.g. scale‐up, printing etc.) can be directly applied to this 2D polymer as well as to covalent organic frameworks.

2D framework materials for energy applications

“…34,35,42 The lateral sizes of the obtained 2DP sheets rely on the size of the single crystals, and the precise thickness control and unambiguous structural denition of the exfoliated nanosheets requires additional effort. 43 Bottom-up on-surface synthesis has also enabled the preparation of various 2DP networks under ultrahigh vacuum condition. [44][45][46][47] Those strategies are generally restricted in terms of lateral size, small crystalline domains (typically tens of nanometers) and high defect density, due to the low mobility of monomers and reactivity at the solid-vacuum interfaces.…”

Advances on Graphene-Based Nanomaterials and Mesenchymal Stem Cell-Derived Exosomes Applied in Cutaneous Wound Healing

“… 48 Lange et al demonstrated that the scale-up of exfoliation could be achieved by shear exfoliation, ball milling or microfluidization. 49 …”

Structural Approaches to Control Interlayer Interactions in 2D Covalent Organic Frameworks

“…Adapted under the terms of the CC‐BY Creative Commons Attribution 4.0 International license ( https://creativecommons.org/licenses/by/4.0). [ 85 ] Copyright 2019, The Authors, published by Wiley‐VCH. c) Chemical structures of PyVg–COF with the photos of the PyVg–COF dissolved in various solvents (top: concentrated solutions under sunlight; bottom: dilute solutions under 365 nm UV light showing the Tyndall effect).…”

“…[ 84 ] The resulting 2D polymers were exfoliated by mechanical exfoliation, by stirring in γ‐butyrolactone and by sonication with sodium cholate, maintaining in the first two cases an optimal degree of crystallinity, while in the case of sonication in the presence of the surfactant a loss of crystallinity was observed. [ 85 ] 2D‐P‐1 could be transformed into a neutral pyridinic parent polymer (2D‐P‐2, Figure 15b) by exposure to gaseous ammonia, which could be exfoliated by sonication with sodium cholate with similar results in terms of quantity and quality to graphene.…”