MOFs based on ZIF-8 deposited on TiO2 nanotubes increase the surface adsorption of CO2 and its photoelectrocatalytic reduction to alcohols in aqueous media

This work describes, the decoration of Ti/TiO2 nanotubes by nanoparticles of ZIF-8 (zeolite imidazole framework-8) grown using a layer-by-layer process. Morphological and crystallographic analyses showed that the TiO2 nanotubes were coated with ZIF-8 nanoparticles around 50 nm in size. Curves of Iph vs. E showed that the incorporation of ZIF-8 at Ti/TiO2 electrodes increased the photocurrent and that the values were dramatically increased in solution saturated with CO2. The CO2 adsorbed on the ZIF-8 formed stable carbamates, as demonstrated by spectroscopic and voltammetric assays. Photoelectrocatalytic reduction of CO2 at Ti/TiO2NT-ZIF-8 electrodes resulted in formation of up to 10 mmol L−1 of ethanol and 0.7 mmol L−1 of methanol in 0.1 mol L−1 Na2SO4, at Eapp of +0.1 V, under UV–vis irradiation at room temperature. Our findings open up new applications of metal-organic frameworks (MOFs) in photoelectrocatalysis for the highly efficient preconcentration and conversion of CO2 in aqueous media at ambient temperature.