Rapid, Massive, and Green Synthesis of Polyoxometalate-Based Metal–Organic Frameworks to Fabricate POMOF/PAN Nanofiber Membranes for Selective Filtration of Cationic Dyes

Abstract

Developing high−efficiency membrane materials for the rapid removal of organic dyes is crucial but remains a challenge. Polyoxometalates (POMs) clusters with anionic structures are promising candidates for the removal of cationic dyes via electrostatic interactions. However, their shortcomings, such as their solubility and inability to be mass−produced, hinder their application in water pollution treatment. Here, we propose a simple and green strategy utilizing the room temperature stirring method to mass produce nanoscale polyoxometalate−based metal−organic frameworks (POMOFs) with porous rhomboid−shaped dodecahedral and hexagonal prism structures. The products were labeled as POMOF1 (POMOF-PW12) and POMOF2 (POMOF-PMo12). Subsequently, a series of x wt% POMOF1/PAN (x = 0, 3, 5, and 10) nanofiber membranes (NFMs) were prepared using electrospinning technology, where polyacrylonitrile (PAN) acts as a “glue” molecule facilitating the bonding of POMOF1 nanoparticles. The as−prepared samples were comprehensively characterized and exhibited obvious water stability, as well as rapid selective adsorption filtration performance towards cationic dyes. The 5 wt% POMOF1/PAN NFM possessed the highest removal efficiency of 96.7% for RhB, 95.8% for MB, and 86.4% for CV dyes, which realized the selective separation over 95% of positively charged dyes from the mixed solution. The adsorption mechanism was explained using FT−IR, SEM, Zeta potential, and adsorption kinetics model, which proved that separation was determined via electrostatic interaction, hydrogen bonding, and π–π interactions. Moreover, the POMOF1/PAN membrane presented an outstanding recoverable and stable removal rate after four cycles. This study provides a new direction for the systematic design and manufacture of membrane separation materials with outstanding properties for contaminant removal.

Fabrication of Loose Nanofiltration Membrane by Crosslinking TEMPO-Oxidized Cellulose Nanofibers for Effective Dye/Salt Separation

“…All results given are averages with standard deviations for at least three samples of each type of membrane. The pure water flow rate was calculated using Equation (1). The dye or salt rejection rate was calculated using Equation (2).…”

“…The rapid development of the global textile industry has heightened the urgency for treating dye wastewater and addressing environmental pollution [1]. Traditional methods for treating dye wastewater often face challenges such as low efficiency, high cost, and the generation of large amounts of by-products [2,3].…”