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.