CBET-EPSRC A Game-Changing Approach for Tunable Membrane Development: Novel Covalent Organic Framework Active Layers Supported by Solvent Resistant Materials

Project: Research project

Project Details

Description

The increasing global demand for safe water and treatment method environmental concerns have led to the development of novel membrane technologies, specifically nanofiltration (NF) and reverse osmosis (RO), because they offer an effective single step rejection of all pathogens and most organic and inorganic contaminants. Despite technical advances, high operational costs and fouling challenges have limited their widespread acceptance. Fouling and water permeability are highly influenced by the physiochemical properties and surface morphology of the polyamide active layer used in state-of-the-art NF and RO membranes. We will create a new class of tunable membranes that combine novel active layers (USA) adhered to robust solvent compatible support media (UK), which will provide high water permeability, selective contaminant rejection, fouling resistance, and chemical robustness.
The US teams will develop active layers based on emerging two-dimensional (2D) polymers known as covalent organic frameworks (COFs). 2D COFs are crystalline, permanently porous materials whose structure, chemical composition, and porosity are set through the rational design of their monomers. COFs will provide separating layers comprising uniform pores with tailored size, shape, and variable chemical functionality, in contrast to the amorphous and empirically optimized RO membranes present in state-of-the-art polyamide active layers. COFs have not been considered deeply for this application because they are typically prepared as insoluble, microcrystalline powders that are not amenable to forming uniform, large-area membranes. The Dichtel group recently achieved a major breakthrough in preparing the first 2D COF films through interfacial polymerization (IP). This method provides large-area membranes (cm2 and above) with precise thickness control (down to 2 nm thus far). The US teams have since collaborated to study the filtration performance of the first COF membranes, which showed mechanical integrity and promising rejection of model organic fluorophores. This nascent effort represents the beginning of a new paradigm for RO membrane design, in which the characteristics of the membrane will be rationally tunable down to the molecular level.
A key finding emerging from the US collaboration is that the commercially available support materials (polysulfone) are incompatible with the organic solvents required to dissolve the COF building blocks. In many instances, exposure to the organic solvents during IP results in the complete dissolution of both polysulfone and polyethersulfone within minutes. This incompatibility with organic solvents is severely limiting the applicability of the IP reactions used to form COFs directly on the support media.
The ICL partners have leading expertise in fabricating membranes for molecular separations in solvent systems, including membranes for nanofiltration in aggressive solvents and under acidic and basic conditions. Through post formation crosslinking, phase inversion membranes of controlled porosity can be created and rendered stable in nearly all common solvents. Thus, the ICL group is uniquely positioned to create supports which can be used by the US teams to prepare COFs in situ. Unlike commercial polymeric supports, the new support media will possess solvent compatibility, exhibit high water permeability, physical durability, a smooth surface for the IP reactions, and have a narrow pore size distribution to prevent the active layer polymer from passing into the treated water.
These novel active layers and robust support
StatusActive
Effective start/end date7/1/176/30/21

Funding

  • University of Illinois at Urbana-Champaign (087147-16468 // CBET-1706219)
  • National Science Foundation (087147-16468 // CBET-1706219)

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