Highly selective CO 2 photoreduction to CO on MOF-derived TiO 2 .

Metal-Organic Framework (MOF)-derived TiO 2 , synthesised through the calcination of MIL-125-NH 2 , is investigated for its potential as a CO 2 photoreduction catalyst. The effect of the reaction parameters: irradiance, temperature and partial pressure of water was investigated. Using a two-level design of experiments, we were able to evaluate the influence of each parameter and their potential interactions on the reaction products, specifically the production of CO and CH 4 . It was found that, for the explored range, the only statistically significant parameter is temperature, with an increase in temperature being correlated to enhanced production of both CO and CH 4 . Over the range of experimental settings explored, the MOF-derived TiO 2 displays high selectivity towards CO (98%), with only a small amount of CH 4 (2%) being produced. This is notable when compared to other state-of-the-art TiO 2 based CO 2 photoreduction catalysts, which often showcase lower selectivity. The MOF-derived TiO 2 was found to have a peak production rate of 8.9 × 10 -4 μmol cm -2 h -1 (2.6 μmol g -1 h -1 ) and 2.6 × 10 -5 μmol cm -2 h -1 (0.10 μmol g -1 h -1 ) for CO and CH 4 , respectively. A comparison is made to commercial TiO 2 , P25 (Degussa), which was shown to have a similar activity towards CO production, 3.4 × 10 -3 μmol cm -2 h -1 (5.9 μmol g -1 h -1 ), but a lower selectivity preference for CO (3 : 1 CH 4  : CO) than the MOF-derived TiO 2 material developed here. This paper showcases the potential for MIL-125-NH 2 derived TiO 2 to be further developed as a highly selective CO 2 photoreduction catalyst for CO production.