Kinetic selectivity in molecular sieve sensors

Project Information

KISSIES

Grant agreement ID: 101045433

DOI

10.3030/101045433

EC signature date 22 April 2022

Start date 1 May 2022

End date 30 April 2027

Funded under

• European Research Council (ERC)

Total cost

€ 2 480 500,00

EU contribution

€ 2 480 500,00

Coordinated by

KATHOLIEKE UNIVERSITEIT LEUVEN
Belgium

Periodic Reporting for period 1 - KISSIES (Kinetic selectivity in molecular sieve sensors)

Reporting period: 2022-05-01 to 2024-10-31

Summary of the context and overall objectives of the project

The KISSIES project ambitiously bridges the realms of porous crystalline materials and sensor technology, marking a pioneering endeavor in the field of selective sensing. The primary motivation behind KISSIES is to utilize the unique properties of Metal-Organic Frameworks (MOFs) toward the development of advanced sensors capable of discriminating volatile organic compounds (VOCs) in complex mixtures. This initiative aims to revolutionize the way VOCs are detected and monitored, addressing critical needs across various applications such as medical diagnostics, air quality assessment, and safety monitoring in industrial environments.

The state-of-the-art in VOC detection currently involves technologies that struggle with selectivity, particularly at low concentrations and in the presence of interfering substances. Traditional sensors, such as metal oxide chemiresistive types, fail to differentiate effectively between similar VOCs due to their reliance on non-selective adsorption principles. KISSIES, however, leverages the kinetic selectivity offered by MOFs—materials characterized by their high internal surface areas and uniform nanopores—which enables significantly enhanced selectivity based on the rates of adsorption and desorption of VOC molecules. Such kinetic properties allow for the precise identification of specific compounds even in the presence of closely related interferents.

By integrating the kinetic selectivity of MOFs into sensor technology, the KISSIES project aims to deliver a groundbreaking solution to the longstanding challenges of VOC detection. The expected impact includes the development of portable, highly sensitive, and selective sensors that can be used for real-time monitoring of environmental and biological markers. Moreover, the cross-disciplinary approach of KISSIES, merging insights from materials science, microelectronics, and data science, not only enhances the technological capabilities of VOC sensors but also promotes innovation across these intersecting fields.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

In the development of sensing elements, we focused on comparing two distinct capacitor geometries—metal-insulator-metal (MIM) and interdigitated electrode (IDE)—for the detection of volatile organic compounds (VOCs) using a metal-organic framework (MOF), specifically ZIF-8, as an affinity layer. Our findings underscore the advantages of utilizing the MIM configuration over the conventional IDE setup in capacitive VOC sensors. Our experiments demonstrated that capacitors with the MIM configuration, which employs a permeable top electrode and the MOF material ZIF-8, exhibit enhanced sensitivity and selectivity, particularly towards polar VOCs. This improvement is due to the direct measurement of changes in the dielectric properties of the ZIF-8 layer without interference from substrate effects that are prevalent in IDE sensors. The MIM sensors achieved a lower detection limit and faster response times, essential for effective real-time VOC monitoring. Through rigorous testing, we established that the thickness of the top electrode is crucial for optimizing the sensor's performance. Thinner electrodes facilitated faster VOC diffusion into the sensing layer, thus enabling quicker sensor responses without sacrificing sensitivity. We also compared the transduction mechanisms utilized in MOF-based sensors, highlighting that the dielectric (capacitive) approach, when applied in the MIM configuration, offers significant advantages over optical and gravimetric methods in terms of both sensitivity and selectivity. Moreover, we have proven the concept of novel sensor technology that harnesses the kinetic selectivity of adsorption in MOFs, for the detection and monitoring of VOCs. These sensors are uniquely capable of detecting VOCs at sub-ppm concentrations, which is crucial for applications such as environmental monitoring, food freshness assessment, and health diagnostics through breath analysis. The primary innovation lies in the sensor's ability to differentiate VOCs not just by their chemical affinity but by their diffusion rates, which vary significantly even among molecules with similar physical sizes due to subtle differences in their interactions with the MOF structure.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

In practical terms, the sensors demonstrated that by carefully controlling the temperature, we can exploit the reversible adsorption properties of a nanoporous material to create a sensor that responds quickly to changes in VOC concentrations, offering both high sensitivity and selectivity. This is particularly advantageous in complex backgrounds where multiple VOCs and other interfering compounds such as water vapor are present. The applications we will focus on include medical diagnostics, air quality assessment, and safety monitoring in industrial environments. In addition, we have pioneered a new method to quickly evaluate how these materials absorb various components, a process crucial for applications like capturing carbon dioxide. Our technique has been successfully tested and has dramatically reduced the time needed for these assessments, from days to mere hours.

To enhance the commercial potential of these scientific advancements, we are currently engaging with the university's technology transfer office to determine which aspects of our innovations might be eligible for patent protection. This effort aims to secure intellectual property rights that could provide a competitive edge in subsequent valorization projects. Concurrently, our research team continues working to further validate the initial promising results. By conducting additional experiments and refining our methodologies, we aim to solidify the robustness and applicability of our findings. One of the researchers involved already indicated to have an interest in leading a valorization effort and has past experience in spin-off creation.

Comparison of capacitive sensors with a conventional IDE geometry vs. an MIM geometry.