Design and Synthesis of Metal-Organic Frameworks for Photocatalytic CO2 Reduction

Sammanfattning

Climate change is one of the most pressing challenges of our time, and the rise in atmospheric CO2 levels is one of the primary causes of this crisis. Large quantities of CO2 are released in the atmosphere through the burning of fossil fuels for energy production, transportation, and various industrial processes. It is therefore urgent to develop technologies that can actively capture CO2 and convert it to less harmful or even useful products. Among the materials being utilized for this purpose, metal-organic frameworks (MOFs) have attracted growing scientific interest. MOFs are porous, crystalline solids in which metal ions are connected by organic molecules, called linkers, to form a three-dimensional network with well-defined pores. A major advantage they have is the ability to tailor their chemical and physical properties by changing the metal or the linker, allowing the design of materials with specific functionalities. In this thesis, a series of MOFs were synthesized solvothermally using 3,3'-diamino-[1,1'-biphenyl]-4,4'-dicarboxylic acid (BPDC-(NH2)2) as the organic linker, with hafnium and magnesium as metal nodes. An Hf-based MOF was successfully synthesized solvothermally and confirmed to be crystalline, thermally stable and microporous with a high surface area. Exploratory syntheses of Mg‑based MOFs highlighted the synthetic challenges of obtaining phase‑pure Mg‑MOFs under the tested conditions, emphasizing the particular advantage of the Hf system as a robust and easily synthesized structure. The ruthenium complex Ru(bpy)2(5,5ʹ‑dcbpy)Cl2· 6H2O was incorporated into the Hf‑MOF to form a Ru@Hf‑MOF that shows photocatalytic activity toward hydrogen evolution and CO2-to-CO reduction under irradiation in the presence of triethylamine as sacrificial electron donor. Overall, the work demonstrates that integrating ruthenium complexes into Hf‑MOFs is an effective approach to creating photoactive porous materials that can be used for syngas production, while outlining future directions for optimization of the process and tailoring of the photocatalysis products.