Multifunctional thin-film nanocomposite membranes comprising covalent organic nanosheets with high crystallinity for efficient reverse osmosis desalination

High-Performance Zwitterionic Nanofiltration Membranes Fabricated via Microwave-Assisted Grafting of Betaine

The thin-film composite (TFC) nanofiltration (NF) membrane is a very important method in solving the water crisis. However, the fabrication and industrialization of high-performance NF membranes still remains challenging. In this work, zwitterionic NF membranes via microwave-assisted grafting of betaine was first proposed. The resulting polyamide layer showed leaflike nanostructures after modification. Because of the enlarged permeation area and enhanced hydrophilicity derived from the unique leaflike structure, the optimal membrane permeability reached 40.8 L m^-1 h^-1 bar^-1. This water permeance was 2.2 times as high as the original polypiperazine-amide membrane, with a Na₂SO₄ rejection maintained at 97.0%. More importantly, the membrane demonstrated excellent selectivity to monovalent and divalent anions. This zwitterionic membrane fabricated by microwave-assisted grafting of betaine provides new insight for industrial scalable NF membranes with great potentials.

Covalent Organic Framework Nanosheets as Reactive Fillers To Fabricate Free-Standing Polyamide Membranes for Efficient Desalination

Mixed matrix membranes (MMMs) have been increasingly utilized in membrane processes. Covalent organic frameworks (COFs) hold great promise as emergent nanofillers to fabricate high-performance MMMs; however, only few studies about COF materials in MMMs have been reported where COFs are all used as nonreactive fillers. Herein, we propose using -NH₂-functionalized COF nanosheets as reactive fillers (rCON) to fabricate MMMs. rCON altered the morphology and chemistry of MMMs by controlling the diffusion rate of piperazine through hydrogen bonding prior to the interfacial polymerization process and inducing the creation of ridges in the MMMs with subsequent increase in surface area (∼24%). rCON was chemically cross-linked to the trimesoyl chloride through amide bonding, subsequently elevating the hydrophilicity (∼35%) and fouling resistance of MMMs. The presence of -NH₂ groups elevated the rCON-PA compatibility, ensuring the high rCON loading of 5 wt % in the MMMs without sacrificing salt rejection. Accordingly, the PA-rCON MMMs exhibited a flux of 46.5 L m^-2 h^-1 bar^-1, which is 6.8 times higher than that of the pristine PA membrane, with a high rejection rate of 93.5% for Na₂SO₄.

A novel mixed matrix membrane framework for ultrafast cation sieving

This work reported a new mixed matrix membrane architecture. Within this structure, cross-linked sulfonated polymers uniformly distributed into the two dimensional channels stacked by graphene oxide sheets. The resulting membranes show ultrafast perm-selectivity towards mono/multiple-valence cations.

Defect-engineered UiO-66-NH2 modified thin film nanocomposite membrane with enhanced nanofiltration performance

Defect-engineered UiO-66-NH₂ was introduced into a polyamide layer to form a thin film nanocomposite (TFN) membrane.