Thesis defense of Valentin Mischke

Metal–organic frameworks (MOFs) provide a modular strategy for engineering materials with targeted properties by combining metal nodes and organic linkers in a defined geometry. This thesis explores the on-surface assembly of MnTPyP on Au(100) into well-defined, reactive two-dimensional coordination networks. Deposition of Co or Ni, followed by mild annealing, converts the initial monolayer into an ordered, commensurate two-dimensional lattice. Structural and spectroscopic measurements show that the porphyrin macrocycle remains largely flat on the surface, while the pyridyl groups tilt out of the molecular plane. In addition, the data indicate on-surface transmetallation, i.e., replacement of Mn by Co in the macrocycle. Core level spectroscopy shows that two cobalt species coexist in the final network, consistent with Co(II) in the macrocycle and a Co(I) state at the pyridyl coordination nodes. Across multiple core levels, network formation induces an almost rigid binding energy shift, indicating modified interface energetics rather than only local bonding changes. Momentum microscopy relates this to the valence electronic structure: ligand-derived states retain recognizable molecular fingerprints, while an additional low-binding-energy contribution develops with weak momentum selectivity, consistent with enhanced electronic coupling within the coordinated lattice. An analogous network is obtained after Ni deposition, with a geometry similar to that of the Co-based system. The Ni 2p_3/2 spectra likewise reveal two chemically distinct components, assigned to Ni(I) nodes and Ni(II) incorporated into the macrocycle, supporting transmetallation also in the Ni case. Finally, the chemical functionality of the coordination nodes is probed by exposing both networks to NO2 and CO. In both systems, gas dosing suppresses the M(I) signature and shifts spectral weight toward higher oxidation states, identifying the +1 node species as the redox-active center, while the macrocycle-bound +2 species remains comparatively inert. Adsorption occurs at room temperature and is reversible upon mild annealing, demonstrating switchable, surface-confined redox chemistry at well-defined coordination nodes.