Coordination-Assistant Chiral Agent Anchoring on Amphiphilic Graphitic Phase Carbon Nitride Membrane for Multiple Molecular Separation.

Abstract

Membranes composed of two-dimensional (2D) materials suffer from low stability and structural swelling and are usually restricted to applications in aqueous systems. Among various 2D materials, graphitic phase carbon nitride (GCN, g-C3N4) has shown great application potential owing to its structural tunability. Herein, we develop a coordination-assisted strategy to regulate the GCN layer spacing and chemical environment via copper ion (Cu2+) coordination-assisted intercalation of enantiopure (1S,2S)-(-)-1,2-diphenyl-1,2-ethanediamine (DPE) between GCN nanosheets. The obtained GCN-Cu-DPE membrane is continuous and intact, free of cracks and pinholes, stable under acidic and alkaline conditions, and exhibits water permeability above 215 L m-2 h-1 bar-1 and a high rejection rate to dye molecules. The membrane is amphiphilicity and thus allows both polar solvent (water) and nonpolar solvent (hexane) to freely pass through. Remarkably, the permeation rate is proportional to the viscosity of the solvent. Benefiting from the chiral space between nanosheets, the GCN-Cu-DPE membrane shows selective permeation of aspartic acid racemate in aqueous systems and limonene racemate in the organic phase. Our work demonstrates a general and promising strategy for chiral membrane fabrication toward high-value-added chiral separation, especially in the pharmaceutical industry.