Remarkable selectivity with which crown ethers served as macrocyclic hosts for various guest species has led to numerous investigations on structure-specific interactions. Successful fabrication of graphene nanomeshes has opened up a plethora of avenues for sensing and separation applications. Embedding crown ether backbones in graphene frameworks can therefore be an interesting strategy for exploring the advantages offered by crown ether backbones, yet having the properties of graphene-based materials. Motivated by the recent success in fabrication of crown ether-based graphene nanopores, herein we investigate their performance toward ion sensing and separation using electronic structure methods. The effect of topology and electronic properties of the nanopore are probed by considering a series of oxygen-based and nitrogen-based graphene crown ethers (crown-n; n = 1-6). Our computations have revealed the excellent alkali ion binding properties of azacrown-based graphene nanomeshes over conventional oxygen crown-based graphene nanomeshes and normal crown ethers. Selectivity in ion transmission through the nanomeshes is demonstrated by employing graphene crown ethers [crown-n (n = 4-6)]. To the best of our knowledge, this article is the first report on azacrown-based graphene nanomeshes and their possible applications in ion sensing and separation, an aspect that we hope will be demonstrated in experiments soon.

Success in single molecule detection using graphene and graphene oxide has opened up numerous opportunities for other 2D carbon-based substrates to be used for applications in sensing and storage. Graphene nanomeshes, in particular, offer excellent platforms as filtration membranes. Molecular adsorption on pristine graphene is governed by weak van der Waals interactions, while considerable binding strengths can be achieved on defective, metal-doped and metal-decorated graphene. Hypothesizing that crown ether-embedded graphene nanopores can bring in a strong electrostatic component toward molecular binding, electronic structure calculations on the binding of NH 3 , H 2 O, and HF on pristine and metal-decorated graphene crown ethers (GCEs), latest addition to the family of graphene nanomeshes are reported. Li + and Ca 2+ decoration on crown-4 and crown-6 GCEs is shown to yield enhanced molecular binding strengths when compared to pristine GCEs and pristine graphene. The per molecular adsorption strengths are found to exhibit a gradual decrease upon addition of molecules. However, the propensity of the molecules to form strong hydrogen-bonded clusters as well as exhibit favorable interactions with the GCEs contributes to a negligible decrease in the per molecular adsorption strengths in some cases. The findings indicate that metal-decorated O-based GCEs are potential substrates for molecular adsorption.