Dissertation defence (Chemistry): MSc Narhari Sapkota

MSc Narhari Sapkota defends the dissertation in Chemistry titled “Metalloporphyrin Based Metal-Organic Frameworks: Syntheses, Characterization and Application in Energy Storage” at the University of Turku on 23 October 2026 at 12.00 (University of Turku, Main building, Tauno Nurmela lecture hall, Turku).

Opponent: Associate Professor Ocean Cheung (Uppsala University, Sweden)

Custos: Adjunct Professor Ari Lehtonen (University of Turku)

Summary of the Doctoral Dissertation:

Metal-Organic Frameworks (MOFs) are a unique class of crystalline porous materials composed of metal ions or clusters (nodes) connected by organic ligands or linkers. Their exceptionally high surface areas, tunable pore structures, and versatile chemical functionalities make them highly attractive for a wide range of applications, including gas storage, energy storage, separation, sensing, and catalysis. Iron porphyrin ligands are particularly attractive because of their rich redox activity, environmental friendliness, and natural abundance. Combining iron porphyrin ligands with lanthanide metal nodes creates a new generation of multifunctional and structurally diverse MOFs that integrate the electrochemical activity of iron centers with the structural stability and unique coordination chemistry of lanthanides.

This study presents the synthesis of a series of MOFs using the iron porphyrin ligand 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin-FeCl (TCPP-FeCl) and lanthanide ions (Ln+3) as metal nodes. Two new types of MOFs were synthesized using L-proline as a co-ligand, which facilitated the formation of high-quality single crystals. These results also demonstrate that amino acids can serve as promising co-ligands for the future synthesis of MOF crystals. Structural characterization revealed that the size of the lanthanide ion significantly influences the morphology, pore size, and surface area of the resulting MOFs. Furthermore, the study showed that the coordination number (C.N.) of the metal nodes plays a crucial role in determining MOF stability. A third MOF was synthesized using benzoic acid as a co-ligand and subsequently employed in the preparation of a poly(3,4-ethylenedioxythiophene) (PEDOT)-MOF composite through the in situ polymerization of 3,4-ethylenedioxythiophene (EDOT) monomers within the MOF pores. In an aqueous LiClO4 electrolyte solution, the MOF/PEDOT composite exhibited enhanced supercapacitive performance, indicating strong potential as an electrode material for future commercial supercapacitors. Electrochemical measurements also confirmed that porphyrin-based MOFs remain stable in aqueous electrolyte solutions, a property that had not been previously demonstrated. This finding further suggests that expensive organic electrolytes may be replaced with low-cost, inorganic, water-soluble electrolytes when using such MOF-based electrode materials.

Additionally, a heme-O₂ binding MOF was successfully synthesized. Unlike previous studies, in which O₂ binding at the porphyrin center of MOFs was observed only at very low temperatures (−78 °C), O2 binding was achieved under synthetic conditions in this work. This advancement highlights the potential of these MOF materials as heme models for the deeper investigation of the functional mechanisms of hemoglobin and other metalloproteins. The findings open new opportunities for the development of porous materials with applications in both energy-related technologies and biomimetic chemistry.