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Geometrical structuring of monolithic metal-organic frameworks (MOFs) components is required for their practical implementation in many areas, including electronic devices, gas storage/separation, catalysis, energy storage as well as bio-medical applications. Despite progress in structuring MOFs, an approach for the precise patterning of MOF functional geometries in the millimeter- to micro-meter depth is lacking. Here, a facile and flexible concept for the microfabrication of complex MOF patterns on large surfaces is reported. The method relies on the engineering of easily-writable sheets of precursor metal oxide nanoparticles. The gas-phase conversion of these patterned ceramic nanoparticle sheets results in monolithic MOF objects with arbitrarily shaped geometries and thicknesses of up to hundreds of micrometers. The writing of complex patterns of zeolitic imidazolate framework-8 (ZIF-8) is demonstrated by a variety of approaches including ion beam, laser, and hand writing. Nanometer-scale patterns are achieved by focused ion beam (FIB). Artless handwritings are obtained by using a pen in a similar fashion to writing on a paper. The pure ZIF-8 composition of the resulting patterns is confirmed by a series of physical and chemical characterization. This facile MOF precursor-writing approach provides novel opportunities for the design of MOF-based devices with applications ranging from micro-fluidics to renewable energy systems.

Mn-Based oxides, particularly CaMn oxides, have recently attracted significant practical interest as a new class of catalyst due to their elemental and structural similarity to the natural oxygen evolving cluster (OEC) in photosynthetic plant cells. However, their performance as oxygen-generating anodes in photoelectrochemical cells has not been studied in detail. In this work, ultra-fine particles of amorphous MnO2, crystalline MnO2 nanorods, Ca2Mn3O8, CaMn2O4 and CaMnO3 were synthesised using a green and scalable mechanochemical method. The particles were comparatively studied as water oxidation photocatalysts in a photo-electrochemical cell at near-neutral pH. The oxides were immobilized on the anode surface using an organic, conducting polymer that facilitated electron exchange and catalytic turnover in a manner similar to redox-active tyrosine in the OEC. The differences in their photocatalytic performances were evaluated in terms of: (1) structural similarities to the natural OEC, (2) Mn oxidation state, (3) crystal structure, (4) specific surface area, (5) electron energy state, and (6) the presence/absence of Ca. The results confirmed the importance of having a local structure that is as similar as possible to the natural OEC cluster, including the presence of Ca. However, it also indicated that it is simplistic to focus only on this feature. The other factors listed above may also play a critical role in performance. Future design of biomimetic catalysts for solar fuel production needs to consider and concurrently optimize all of the relevant influences.

The effects of V and Ce concentrations (each varying in the 0–100% range) in vanadia–ceria multiphase systems are investigated for synthesis gas production via thermochemical redox cycles of CO2 and H2O splitting coupled to methane partial oxidation reactions. The oxidation of prepared oxygen carriers is performed by separate and sequential CO2 and H2O splitting reactions. Structural and chemical analyses of the mixed-metal oxides revealed important information about the Ce and V interactions affecting their crystal phases and redox characteristics. Pure CeO2 and pure V2O5 are found to offer the lowest and highest oxygen exchange capacities and syngas production performance, respectively. The mixed-oxide systems provide a balanced performance: their oxygen exchange capacity is up to 5 times higher than that of pure CeO2 while decreasing the extent of methane cracking. The addition of 25% V to CeO2 results in an optimum mixture of CeO2 and CeVO4 for enhanced CO2 and H2O splitting. At higher V concentrations, cyclic carbide formation and oxidation result in a syngas yield higher than that for pure CeO2.