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This PhD research presents a novel approach to Carbon Capture and Utilization (CCU), focusing on the transition from traditional high-pressure methods to more sustainable low[1]pressure and low-concentration systems. By capturing carbon dioxide (CO₂) from real-life sources, such as biogas and diluted CO₂, the project demonstrates how Direct Air Capture (DAC) can be integrated into CCU strategies under mild conditions. A key innovation is the hydrogenation of CO₂ with hydrogen gas (H2) at 1 bar and 30°C, much milder than conventional high-pressure methods. Using homogeneous catalysis with a ruthenium-based catalyst and ionic liquid (IL) — which serves as both solvent and base, offering a safer alternative to volatile organic compounds (VOCs) — the captured CO₂ is converted into formic acid, a Liquid Organic Hydrogen Carrier (LOHC) with significant potential for hydrogen storage and renewable energy applications. The research also investigates the dehydrogenation of formic acid at 85°C, where H₂ and CO₂ are produced as the only products with no traces of carbon monoxide (CO). This reversible process highlights the crucial role of formic acid as a carrier for both hydrogen storage and release, representing a key advancement for renewable energy systems. This work demonstrates the ability to utilize low-concentration CO₂ in a practical and scalable way, showcasing that CCU can be applied to real-life diluted systems and not just high-purity sources. By integrating DAC and transitioning from high pressure to low pressure, the research provides a sustainable and scalable solution for CO₂ utilization, contributing to the reduction of emissions while producing valuable products from CO₂
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\n Principal Supervisor: Associate Professor Martin Nielsen, DTU Chemistry Co-supervisor: Professor Shoubhik Das, University of Bayreuth, Germany Professor Anders Riisager, DTU Chemistry Examiners: Professor Tom Welton, Imperial College London, England Associate Professor Jiwoong Lee, Copenhagen University Chairperson:
\nAssociate Professor Jerrik Mielby, DTU Chemistry