Polymers in search of the magic filter

When did you join EPFL? Can you tell us about your team and your current research?

I have been a Professor at EPFL since 2016 when I took over the leadership of the LAS. This laboratory is part of the Institute of Chemical Sciences & Engineering (ISIC) of the Faculty of Basic Sciences (FSB). The group is quite diverse and includes materials scientists, chemists and mechanical engineers from all over the world. About ten nationalities are represented. My research group is engaged in materials chemistry and engineering at the Angstrom scale (10-¹⁰ metre) with a view to designing very high efficiency membranes capable of filtering molecular scale elements like CO2. This is a way of reducing carbon dioxide emissions, as the gas can be captured in the post-combustion phase (in stacks) before it enters the atmosphere. The captured CO2 can then be either recycled or stored as a gas or liquid until it can be used for other applications. This process is called sequestration.

We are looking for solutions that are economically attractive so that they can be made available to all companies that emit greenhouse gases. This is why we have focused our research on nanoporous and two-dimensional membranes. By nanoporous, we mean capable of filtering elements of the size of a nanometre and two-dimensional means of a thickness of the order of a nanometre. We want to create membranes that allow high flow rates and that only let certain gas molecules through. These membranes are environmentally-friendly, the manufacturing process does not generate waste, and they are currently considered one of the most energy-efficient solutions for reducing carbon dioxide emissions. We are looking for the perfect molecular filter!

You seem to have found it as you have developed a new class of high-performance membranes for carbon capture. How do they work?

Our membranes are based on filters made of graphene (a material whose discovery led to a Nobel Prize) and a polymer. We have succeeded in perforating the graphene so precisely that it now only allows carbon dioxide (CO2) molecules to pass through, but not, for example, nitrogen (N2). In this way, when the filter is exposed to a mixture of CO2 and N2, it will only capture the CO2, allowing us to recover a molecule free of impurities.

What role do polymers play in this membrane?

Their role is crucial. We have used a "CO2philic" polymer film. Its function is to increase the concentration of CO2 and guide it towards the holes in the graphene.

We have developed a process in which we laminate this polymer film onto graphene so that a nanometre-thick membrane with a large surface area can be produced without cracks or tears. We are therefore able to produce membranes to meet all the demands of industry.

How is it superior to existing membranes?

First of all, we have managed to achieve an excellent flow rate. This means that we can filter a significant flow of CO2. In our scientific jargon, we talk about permeance. This is the ability of a wall to let water vapour through. Water vapour should be considered as a master standard. The higher the permeance, the smaller the required membrane surface. As a result, the investment cost will be lower for interested industries.

So, when will these membranes be on the market?

We estimate that the time to market is 2 to 3 years. We are currently building a pilot-scale demonstrator to capture CO2 from various sources (flue gas, biogas, etc.). The demonstrator should be operational by the end of 2022 and should meet market expectations. We are already working with a number of industrial partners, including Gaznat, Shell and local Swiss SMEs specialising in biogas and waste incineration.

Kumar Varoon Agrawal’s academic background

• Born in India.
• Undergraduate degree in Chemical Engineering at IIT Bombay in 2005.
•  Until 2008, Global Research & Development division of Procter & Gamble in Japan.
• PhD in Chemical Engineering at the University of Minnesota (United States) in Professor Michael Tsapatsis’ group. Thesis on the isolation of highly crystalline two-dimensional zeolite nanosheets.
• 2014, postdoctoral associate in the Strano group of the Massachusetts Institute of Technology (MIT). Study of the effect of nanoconfinement during fluid transition phases.
• Recipient of the FRI/John G. Kunesh Award of the Separations Division of the American Institute of Chemical Engineers (AIChE), Young Membrane Scientist Award of the North American Membrane Society, the European Research Council Starting Grant, the Swiss National Science Foundation Assistant Professor Energy Grant, among others.