Pseudomorphic replication as enabling technology for porphyrinic metal–organic framework thin film growth

Metal–organic framework (MOF) thin films, comprising different metalloporphyrins, are synthesized on copper and gas diffusion electrodes (GDEs) via pseudomorphic replication. Thereby, a metal oxide layer, applied by atomic layer deposition, is transformed into a MOF thin film through conventional or microwave-assisted heating upon metalloporphyrin addition. The synthesis of porphyrinic Al 2 (OH) 2 MTCPP (M = Co, Cu, Fe, Zn, H 2 ; H 2 TCPP refers to 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin) metal–organic framework (MOF) thin films is demonstrated. Combining atomic layer deposition (ALD) and pseudomorphic replication (PMR), such thin films were for the first time grown on metallic copper substrates and gas diffusion electrodes (GDEs). The PMR process transforms an ALD-applied metal oxide layer into a MOF thin film upon exposure to a metalloporphyrin linker. Reflecting substrate requirements, MOF thin films were synthesized via conventional solvothermal heating for copper substrates or microwave-assisted heating for GDEs, with the latter significantly reducing reaction times from days to minutes. Characterization by scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the structural integrity and uniformity of the films. This work expands the arsenal of methods that are available for integrating MOF thin films into functional, in particular, porous electrode materials, paving the way for future advancements in catalysis and electrochemical applications.