Chitosan Carbon Dot Cross-linked Layered Double Hydroxide-Coated High-Performance Thin-Film Nanocomposite Membranes for Facile CO ₂ Separation

The quest for carbon capture has become imperative to combat growing environmental pollution, which has led to the evolution of numerous cutting-edge technologies. Membrane technology has gained widespread application in carbon capture owing to its advantageous features, including high separation efficiency, scalability, energy efficiency, low environmental impact, and ease of operation. Herein, a thin-film nanocomposite (TFN) membrane laminated with ZnFe-layered double hydroxide (LDH) and chitosan carbon dots (CDs) has been developed for the separation of CO2/N2 and CO2/CH4 gas mixtures. LDH is hydrothermally synthesized over a polymeric porous support, which is further cross-linked with CD using glutaraldehyde as a cross-linker. The designed membrane provides the highest CO2 permeability of 6559 Barrer with CO2/N2 and CO2/CH4 selectivities of 32.4 and 45.8, respectively, which surpasses the 2008 upper-bound limit. The membrane also exhibits excellent separation performance with separation factors of 15.7 and 35.1 for CO2/N2 and CO2/CH4 gas mixtures, respectively. The excellent CO2 separation performance of the designed membrane can be explained by the synergistic effect of the CO2-phillic nature of amine CD and the narrow interlayer spacing in LDH. Enhancement in mechanical stability as well as durability of the designed TFN membrane is observed after reinforcement of the CD/LDH layer over a porous polymeric support. The current work is highly anticipated to address the growing energy demand associated with energy-intensive conventional gas separation processes.