(414a) Photocatalytic Conversion of Carbon Dioxide With Water On Ti-Based MOFs: An Experimental Investigation

Since Fujishima and Honda first demonstrated photocatalytic water splitting in 1972^[1], numerous investigators have extended the idea into many other semiconductors and photoreactions. Utilizing solar energy to facilitate photocatalytic conversion of carbon dioxide (CO₂) with water (H₂O) to fuels and chemicals such as CO, CH₄, CH₃OH holds great potential as a sustainable alternative energy source and as a promising method to reduce pollution and global warming.    

In spite of the large number of studies and materials investigated for photocatalytic CO₂ conversion, efficiencies achieved to date have been very small and much work remains to be done to overcome the limitations. Metal-organic frame works (MOFs) are perhaps uniquely suited to address CO₂ capture and photocatalytic conversion because of their exceptional porosities, tunable pore sizes and chemical structure. The principle of reducing CO₂ in a MOF using UV radiation has recently been demonstrated by doping a photocatalyst moiety into a MOF^[2].  Researchers at USF have been developing Ti-based semi-conductive MOFs that are photo-active in the visible light range. 

In this study, we evaluated the photocatalytic activity of a Ti-based metal-organic framework in a gas-phase CO₂ reduction reaction using a robust photoreactor system. The reactor system has a small volume (<15ml) with the ability to control temperature, pressure and reaction type (batch or flow reactor).  Photoreaction efficiency, product conversion and selectivity of MOF photocatalysts are analyzed in comparison to conventional TiO₂ (P-25). Reactor conditions, including temperature and pressure, were optimized to improve reaction kinetics and the conversion of CO₂ and water to the desired products. 

References:

[1] Fujishima, A., & Honda, K. (1972). Electrochemical Photolysis of Water at a Semiconductor Electrode. [10.1038/238037a0]. Nature, 238(5358), 37-38.  

[2] Wang, C., Xie, Z., deKrafft, K. E., & Lin, W. (2011). Doping Metal–Organic Frameworks for Water Oxidation, Carbon Dioxide Reduction, and Organic Photocatalysis. Journal of the American Chemical Society, 133(34), 13445-13454. doi: 10.1021/ja203564w