Electrocatalysis in confinement: metal-organic frameworks for oxygen reduction

Hoefnagel, M.E. (2025)

Doctoral Thesis

The confinement of molecular catalysts in metal-organic frameworks has the potential to lead to significant improvements in selectivity, long term activity and catalyst stability. The efficiency of electrocatalysis in MOFs is expected to be limited by either the activity of the catalyst, mass transport through the framework or electron transfer. Although initial strategies to improve electron transfer throughout MOFs have been described, major knowledge gaps still exist. For example, it remains unclear how electron transport in MOFs affects electrocatalysis and how mass transport of reactants limits electrocatalysis, and what the effects are of confinement in a MOF on the catalyst structure. It is expected that these research questions remain an important area of research in the future. The research described in this thesis concerns the oxygen-reduction catalyst Cu-tmpaCOOH confined in MOFs. The Cu-tmpa catalyst and its catalytic performance are well characterized.[117–119] The main challenge regarding this catalyst concerns its long-term stability, which may be improved through immobilization in MOFs. The research described in this thesis addresses a number of the challenges mentioned in Section 1.7. In Chapter 2 the effect is discussed of incorporation of the Cu-tmpaCOOH catalyst in a MOF on its catalytic activity and selectivity. In Chapter 3 the effect of confinement on the catalyst itself is described. The homogeneity of the catalyst and the identity of the true active species are discussed. Chapter 4 discusses the effect of electron transport through the MOF on the catalyst and its catalytic performance. This chapter provides a comparison between a redox inert MOF and a MOF containing redox-active linkers. The efficiency of electron transfer to the catalyst, the homogeneity of the catalyst and catalytic activity and selectivity have been investigated. Chapter 5 contains a detailed discussion of the effect of pH on charge transport in redox active MOFs. Chapter 6 provides a summary of the results in this thesis as well as a conclusion and outlook.

• Electrocatalysis
• Metal-organic frameworks
• Oxygen reduction
• Electrochemistry
• X-ray absorption spectroscopy

• All authors: Hoefnagel, M.E.
• Supervisor: Hetterscheid, D.G.H.; Bouwman, E.
• Committee: Ubbink, M.; Bonnet, S.A.; Geuchies, J.J.; Morris, A.J.; Pullen, S.
• Qualification: Doctor (dr.)
• Awarding Institution: Leiden Institute of Chemistry (LIC), Faculty of Science, Leiden University
• Date: 2025-12-05