We create molecularly-selective synthetic membranes that can provide attractive transport properties in scalable ultra-thin hollow fiber devices for sustainable separation processes.

Research Overview

Distillation and other thermally-driven separations are extremely energy-intensive consuming roughly half of U.S. industrial energy use. Transport in molecularly-selective membranes is driven by chemical potential gradient, and membrane-based separations can be more energy-efficient with significantly lower carbon dioxide emissions. The Sustainable Separations Lab at the University of Maryland aims to reduce the carbon dioxide footprints and enhance the sustainability of large-scale separations by creating molecularly-selective synthetic membranes that can debottleneck or replace thermally-driven separations.

To achieve this goal, our research focuses on:

  1. Molecular-scale design of materials chemistry and structure

  2. Understanding transport fundamentals in new membrane materials

  3. Translating new membrane materials to scalable hollow fiber devices with ultra-thin separation layers

Enhancing the energy efficiency and sustainability of large-scale separations by molecularly-selective synthetic membranes

Comparing nanoporous and polymeric membranes for challenging molecular separations (link to paper)

Molecular-Scale Design of Materials Chemistry and Structure

The first revolution of sustainable separations was membrane-based desalination, which occurred in the 1960s as a result of the invention of flexible polymeric membranes. We believe the next revolution of sustainable separations will be enabled by membranes based on advanced materials with rigid nanopores. These nanoporous materials can provide excellent transport properties-productivity (permeability) and separation efficiency (selectivity) for closely-sized/shaped molecular pairs under challenging feeds that can compromise the separation efficiency of flexible polymeric membranes (see left for example).

The Sustainable Separations Lab creates advanced nanoporous materials with attractive intrinsic transport properties for target molecular pairs through molecular-scale design of materials chemistry and pore structure. Membrane selectivity is governed by diffusion selectivity and sorption selectivity. While both are crucial, we primarily focus on designing nanoporous materials with tunable pore structures and diffusion selectivity.

Understanding Transport Fundamentals in New Membrane Materials

Diffusion in nanoporous materials is an important and fundamentally interesting topic in both separation and catalysis sciences. Our lab will contribute to building the connections between pore structures (dimension/topology/flexibility) and guest molecule diffusivity/diffusion selectivity in nanoporous materials. Such an understanding is useful to guide the creation of new membrane materials with tunable transport properties for separation of target molecular pairs. The Figure on the right shows diffusion measurements in thermally-tailored metal-organic frameworks, which assisted the design of new membrane materials.

The Sustainable Separations Lab will develop macroscopic experimental tools to study diffusive transport in nanoporous membrane materials (e.g. nanoporous carbon, inorganic-organic hybrid molecular sieves, zeolites, etc.). We also seek collaborations with other labs on/off campus to study transport fundamentals using mesoscopic and microscopic methods.

Measuring diffusion in thermally-tailored metal-organic frameworks (link to paper)

Translating New Membrane Materials to Scalable Hollow Fiber Devices with Ultra-Thin Separation Layers

Creating nanoporous membrane materials with attractive intrinsic transport properties is crucial; however, more is required to achieve our goal. To enable large-scale separations, the cost and footprint of membrane separators must be minimized. Therefore, translating nanoporous membrane materials to scalable devices with high packing efficiency is also crucial. Hollow fibers are tubular devices (diameter~100-400 micron) with ultra-high packing density up to 20,000 m2/m3. To further minimize the cost of hollow fiber membrane separators, nanoporous materials must be processed into defect-free ultra-thin separation layers to provide attractive product flux.

The Sustainable Separations Lab leverages our strong expertise in design and fabrication of scalable and tunable hollow fiber devices for separation, catalysis, and other energy-related applications. The picture on the left shows lab-scale manufacture of hollow fiber membranes with production rate up to 200-300 m2/hour.