Enhancing the perm-selectivity of thin-film nanocomposite membranes intercalated with cyclodextrin-chelated Metal-Organic Framework via modulated interfacial polymerization

Abstract

Nanofiltration (NF), an exceedingly promising technology, has been extensively implemented within the domain of desalination. The pursuit of optimizing water permeance, while upholding outstanding rejection rates to ameliorate the vexing permeability-selectivity trade-off effect, has raised tremendous concerns. Herein, a novel approach has been proposed, involving the construction of a cyclodextrin-chelated Metal-Organic Framework (MOF) interlayer through vacuum-assisted filtration, aimed at orchestrating the interfacial polymerization (IP) process and sculpting the membrane morphologies of polyamide membranes. The results demonstrated that cyclodextrin-chelated MOF interlayer produced a “gutter” effect for faster water transport and enhanced the interaction of the substrate and PA layer. Simultaneously, the interlayer helped to alleviate the diffusion rate of piperazine (PIP) via the interactions (e.g., hydrogen bonds, electrostatic attraction and steric hindrance) between interlayer and PIP, leading to a lower cross-linking degree and a defect-free thinner active layer. Meanwhile, cyclodextrin with intrinsic nano-cavity created more free volume for water transport inside the polymer. Furthermore, the crumpled interlayer established a hydrophilic undulated interface, followed by the generation of micro-wrinkled polyamide layer with larger filtration areas. The optimal membrane exhibited a high permeability of 39.59 L/m² h bar, nearly 6.5 times than that of the original membrane, while maintaining a remarkable Na₂SO₄ rejection of 95.71 %. The strategic deployment of cyclodextrin-chelated MOF interlayers in membrane modification held the potential to efficaciously mitigate the trade-off effect, thereby presenting a promising avenue for the realization of highly-efficient desalination processes.