Purifying Water from Boron Contamination with Highly Selective Metal-Organic Framework (MOF) Membranes

Purifying Water from Boron Contamination with Highly Selective Metal-Organic Framework (MOF) Membranes
Zachary Smith, Joseph R. Mares Career Development Professor, Department of Chemical Engineering

Period of performance: 

September 2018 to August 2020
MOF, Metal Organic Framework, MOFs, water purification, desalination, Boron, water quality

Abstract: 

This project seeks to leverage techniques and expertise at the interface of inorganic chemistry, materials science, and chemical engineering to achieve technical breakthroughs in water purification.  The strategy is to use water-stable metal-organic frameworks (MOFs) that have well-defined pore structures that can be engineered for the efficient removal of small neutral contaminants such as boron from water.

Boron is an essential micronutrient for both plants and animals, but becomes toxic at higher concentrations.  However, due to its small molecular size and un-charged chemical structure, it is particularly difficult to remove with standard water purification technologies.  Current desalination membrane technologies that operate with amorphous polymers cannot effectively remove boron from water due to its small molecule size and absence of ionic charge under normal operating conditions.   This project seeks to meet this challenge by developing highly selective membrane materials and membranes with near-perfect boron rejection for water purification.

MOFs carry particular qualities that make them well-suited for highly selective water purification and desalination.   The formation of materials with molecularly tuned pore apertures in combination with precisely designed chemistry allow MOFs to effectively reject small neutral molecules via size exclusion and solute-framework interactions.   However, the design and synthesis of effective MOFs for discrimination of small molecules in aqueous conditions has not been well investigated.   In order to address this critical need, this project will focus on the design, synthesis, and characterization of water-stable MOF materials with an optimized structure suitable for boron removal.   In addition, Smith and his team will explore new methods to fabricate these selective MOF materials into membrane separators.  

The development of this technology could provide a solution to the challenge of the low selectivity of current state-of-the-art polymer-based membranes.  These MOF membranes, once developed, could provide stable separation performance in aqueous environments while still providing high water permeability and high rates of boron rejection.   The success would prove significant for water purification and desalination industries and, more importantly, provide a solution to an environmental challenge that is currently unmet by known water filtration polymers today.