Water Quality Monitoring Using Quartz Sensors Modified With Metal-Organic Frameworks

Methane, a potent greenhouse gas, poses a major climate challenge. While it’s wellknown that sources like fossil fuels and “cow burps” release methane, fewer people realize that water bodies such as wetlands and abandoned offshore oil wells, also contribute significantly. Wetlands, for example, release methane as permafrost thaws, while small leaks from old, unused oil wells can fill nearby water with methane and other pollutants, posing risks to marine life and the environment. Until now, measuring methane dissolved in water has been tough, as most sensors are designed to detect methane in the air, not in complex water environments.

To tackle this, we are exploring new materials called metal-organic frameworks (MOFs). Think of MOFs as customizable super-sponges made of metal and organic building blocks, like LEGO blocks. Their structure can be carefully adjusted to "trap" only certain types of molecules, like methane, even in a mix with other molecules. By combining MOFs with a sensitive detector called a quartz crystal microbalance (QCM), which measures tiny changes in weight as molecules stick to it, we have created sensors that can pick up on even the smallest traces of methane in water (as little as 100 parts in a billion parts of water) in less than a minute.

Imagine these sensors as a kind of molecular detective, designed to pick up unique “fingerprints” for different molecules. The sensor developed in this research can not only detect methane but also distinguish it from other molecules, like carbon dioxide. This innovation goes beyond just methane. The same approach was used to detect other harmful chemicals like benzene and toluene in water. Building on this work, we can envision a future where small, portable sensors deployed in lakes or rivers could warn us about pollutants in real-time, allowing quick action to protect our environment. By helping us keep a closer watch on hidden methane sources and other pollutants, this technology opens a window to a cleaner, safer future for our planet.

Principal supervisor: Associate Professor Jonas Sundberg

Co-supervisor: Professor Simon I. Andersen Co-supervisor: Professor Kasper S. Pedersen

Examiners: Associate Professor Stefania Grecea, Van 't Hoff Institute for Molecular Sciences, University of Amsterdam Associate Professor, Klaus Koren, Department of Biology - Microbiology, Aarhus University Senior Scientist Ali Akbar Eftekhari, DTU Sustain

Chairperson at defence: Associate Professor Andreas Kaiser, DTU Energy