Investigating the impact of metal ion variations in terephthalate metal–organic frameworks on the organic solvent nanofiltration performance of mixed matrix membranes

Abstract

Nano-fillers integrated into mixed matrix membranes (MMMs) present promising alternatives for organic solvent nanofiltration (OSN). In this work, our objective is to enhance OSN performance by incorporating terephthalate metal-organic frameworks (M-BDC, where M = Zr or Cu) into a P84 matrix to fabricate M-BDC/P84 composite MMMs. This work focuses on the influence of metal cluster variation on particle size, pore size distribution, and specific surface area of M-BDC, while systematically investigating the impact of M-BDC addition on OSN performance and underlying separation mechanisms. The synthesized membranes underwent comprehensive characterization using SEM, XRD, ATR-FTIR, contact angle, zeta potential, and thermogravimetric analysis. Significantly, all MMMs exhibited superior permeance and methyl blue (MB) rejection compared to P84 membranes. This enhancement is attributed to the improved interfacial contact between M-BDC and P84, as well as their effective dispersion within the membrane matrix. Interestingly, comparative analysis between Cu-BDC/P84 and Zr-BDC/P84 MMMs revealed the latter's superior permeance, attributed to its larger pore size and surface area. The resulting MMMs demonstrated outstanding MB rejection (>96.7%) with ethanol permeance of 21.5 and 19.0 LMH/Bar for Zr-BDC/P84 and Cu-BDC/P84 MMMs, respectively. Furthermore, the stable performance of M-BDC-based MMMs during prolonged MB/ethanol operation underscores their potential significance in the field of OSN, providing valuable insights for future membrane design and application.