Innovative 2D Membrane Architecture for Advanced Chiral Molecules Separation

Membranes play a crucial role in various fields of technology, including water treatment and chemical separation. However, conventional polymer membranes are reaching a performance limit due to the trade-off between permeability and rejection. Thus, the search for new materials combining high permeability with efficient rejection for next-generation separation membranes has become essential. The stacking of two-dimensional (2D) nanosheets in laminar membranes to create nano-channels has attracted considerable interest, both fundamental and practical, for separation technologies [1]. 2D materials, in particular, have thus proved to be promising candidates for these applications, thanks to their large side-loading area and high surface density, which offer unique advantages for membrane separation [2].

In this context, our work focuses on the functionalization of molybdenum disulfide nanosheets (MoS₂) with chiral molecules, such as (R)-(+)-α-Methylbenzylamine and (S)-(-)-α-Methylbenzylamine. This approach aims to exploit their distinct properties for the recognition and selective separation of enantiomers. By integrating chiral ligands on the surface of MoS₂ nanosheets, we demonstrate how chirality influences molecular interactions and promotes the separation of optically active compounds.

We will present our recent advances in the manufacture and characterization of innovative membranes. X-ray diffraction (XRD) analysis confirmed the functionalization of the nanosheets, increasing the inter-sheet space from 6.2 Å to 10.7 Å, reflecting the molecular interactions that occurred during synthesis. Scanning electron microscopy (SEM) images has confirmed the maintenance of the lamellar structure.
Furthermore, we will discuss the results of direct osmosis performance tests, which demonstrated flow rates in excess of 10 L/m²/h^-1 with these membranes. Rejection tests were carried out on our membranes with a racemic solution of tryptophan, and analyses revealed enantiomeric selectivity, confirmed by circular dichroism (CD) analyses. Quantification of this rejection by chiral high-performance liquid chromatography (HPLC) shows a selectivity rate in excess of 70%. These results pave the way for promising applications in water treatment, as well as in the environmental and pharmacological fields. In conclusion, this study highlights the potential of functionalized 2D materials for innovative applications in sustainable chemistry and environmental technologies.

[1] Shen, J. et al.Nature Review Materials 2021, 6, 294-312.
[2] Ries et al.Nature Materials 2019,18(10), 1112–1117.