Supramolecular Surface Charge Regulation in Ionic Covalent Organic Nanosheets: Reversible Exfoliation and Controlled Bacterial Growth

Abstract

Poor control on the exfoliation of covalent organic frameworks (COFs) remains a disadvantage for their application as two‐dimensional nanosheets. An equally important problem is the reversible control at the available surface charges on COFs. Herein, a strategy for the reversible exfoliation, re‐stacking, and surface‐charge control of a propidium iodide based ionic covalent organic framework, PI‐TFP, using cucurbit[7]uril (CB[7]) induced molecular recognition, is reported. The surface charge on PI‐TFP facilitates its initial self‐exfoliation. However, complexation with CB[7] resulted in re‐stacking with concomitant decrease in zeta potential from +28±3.0 to +0.004±0.003 mV. Addition of 1‐adamantylamine hydrochloride (AD) facilitates decomplexation of PI‐TFP from CB[7], resulting in exfoliation and an increase in zeta potential to +24±3.0 mV. Such control on the exfoliation, re‐stacking, and the associated regulation of the surface charge in PI‐TFP was exploited for controlling bacterial growth. Thus, the activity of E. coli and S. aureus bacteria obtained with the self‐exfoliated PI‐TFP could be reversibly controlled by the CB[7]/AD pair.

2D framework materials for energy applications

“…87 In a follow up study the related propidium iodide cationic COF was prepared and it readily self-exfoliated in water to sheets with an average thickness of 1.6 nm. 88 Interestingly, this material can be restacked by the use of a macrocyclic host, in this case cucurbit [7]uril, through complexation of the quaternary ammonium groups on the propidium side groups. Addition of 1-adamantylamine hydrochloride leads to decomplexation and the material exfoliates again.…”

Nature‐Inspired Construction of MOF@COF Nanozyme with Active Sites in Tailored Microenvironment and Pseudopodia‐Like Surface for Enhanced Bacterial Inhibition

“…Inspired by these unique features, we envision that tailoring microenvironment around the active sites of MOF‐based nanozymes via installing specific functional groups and constructing favorable spatial structure may be a promising strategy to make them more closely mimic the natural enzymes. Covalent organic frameworks (COFs), as crystalline organic porous polymers with customizable composition and controlled morphology, have been exploded as salient materials for diverse catalytic reactions and many facets of the biomedical fields [30–38] . For example, several COF‐based hybrid materials with high catalytic performance have been reported, the resultant hierarchical structures could promote the adsorption of reactant substrate molecules [39–41] .…”

2D Covalent Organic Frameworks for Biomedical Applications

“…Recently, Mal et al have developed a propidium iodide based 2D-iCONs which efficiently inhibit bacterial growth once exfoliated while chemical mediated restacking of the nanosheets switch to loss of their anti-bacterial activity which can further be regenerated by removing the chemical providing a control over bacterial growth. [138] Other sets of anti-bacterial 2D COFs are reported by Liu et al which can kill bacteria in presence of light. [139] Authors have demonstrated that 100 µg/L of these two 2D COFs can kill 90% of bacteria when illuminated with light for 60-90 min.…”