CO2 capture and photocatalytic reduction using bifunctional TiO2/MOF nanocomposites under UV–vis irradiation

Abstract

Abstract TiO 2 nanosheets and metal-organic framework (NH 2 -UiO-66) were effectively coupled via an in‐situ growth strategy to form bifunctional materials for the combined capture and photocatalytic reduction of CO 2 under UV–vis light irradiation. This was done to take advantage of the high CO 2 adsorption capacity of the MOF and the photocatalytic properties of pre-formed TiO 2 nanosheets in a single material. The prepared materials were thoroughly characterized using a variety of techniques. They were subsequently tested for CO 2 adsorption and CO 2 photocatalytic reduction using a heterogeneous gas/solid set-up to imitate both CO 2 capture and fixation in a single process. The adopted synthesis process allowed the development of a tight interaction between TiO 2 and NH 2 -UiO-66 forming a heterojunction, while maintaining both the high CO 2 uptake and porosity of NH 2 -UiO-66. The nanocomposites were proven durable and significantly more efficient in reducing CO 2 to CO than their single components. Photocatalytic activity was greatly affected by the nanocomposites composition with the optimum TiO 2 content doubling the CO evolution rate compared with the pure TiO 2 . The improved photoactivity was assigned to the enhanced abundance of long lived charge carriers, as revealed by transient absorption spectroscopy (TAS). This most likely occurred due to the effective charge transfer via interface. A possible mechanism is discussed on the basis of the combined catalytic, spectroscopic and CO 2 adsorption results.