Titanium dioxide (TiO₂) is one of the most used photocatalysts, but it has some limitations, such as its low surface area and high electron-hole recombination rate. These limitations can be resolved by the coupling of a metal-organic framework (MOF). In contrast to monofunctional photocatalysts, MOF-based composites can yield improved molecule selectivity and visible light activity. MIL-101(Cr) was chosen as the MOF component due to ease of modifications to its framework and its enhanced CO₂ uptake capacity. In this work, two different strategies to mediate MOF growth onto the surface of TiO₂ are being investigated and will be presented. Following a direct interface approach, core-shell particles were obtained by a hydrothermal synthesis composed of MOF starting materials and anatase TiO₂, in which a MOF shell grew directly in contact with the semiconductor. The effect of the concentration of TiO₂ on the formation of core-shell particles was investigated. As the concentration of TiO₂ increased from 20% to 60% compared to a fixed concentration of MIL-101(Cr) starting materials, more MOF@TiO₂ particles with flower-like morphology were seen throughout the sample. Moreover, the second strategy investigated followed an indirect approach, which consisted of growing MOF particles on carboxylate terminated TiO₂ by applying a step-by-step self-assembly process. Here, metal ions were coordinated to the carboxylate terminated TiO₂ followed by addition of the organic ligand. Further investigations will be conducted by using hollow TiO₂ and amine modified MIL-101(Cr), which has been a successful material to mitigate the photocatalyst limitations and enhancement of CO₂ binding sites on MIL-101(Cr), respectively. As a result of the MOF-based materials design that combines the properties of MOF and TiO₂, this work provides the means for improving photocatalytic CO₂ conversion.

Hannah Ramos

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