Phase-dependent selectivity control over TiO2 in the photocatalytic oxidation of bio-polyols

Photocatalytic oxidation shows great potential in the valorization of biomass under mild conditions, while the selectivity control is particularly challenging for the complex and reactive bio-polyols. Herein, we report a selective photocatalytic process to convert bio-polyols into formic acid (FA) or carbon monoxide (CO) by control-ling the phase of TiO2. The bio-polyols are facially oxidized to formic acid (FA) which is stable over rutile and could be dehydrated to CO over anatase TiO2. Through controlling the phase, FA or CO could be obtained from a wide range of bio-polyols with selectivity up to 63% or 52%. Our studies elucidate that the phase-dependent selectivity is essentially derived from the difference in the adsorption configuration of FA. In situ Fourier transform infrared spectro-scopy (FTIR) and density functional (DFT) calculations were used to study the FA decomposition process on the surface of TiO2. The phase-dependent FA decomposition is mainly derived from the different surface geometry, which affects the configuration of FA adsorption. Molecular adsorbed FA on anatase favors the dehydra-tion of FA to CO while bidentate dissociated adsorption of FA on the rutile phase is inert to be further converted. This work provides a new horizon to the design of photocatalytic systems for biomass conversion.

Automated summary

Photocatalytic oxidation of bio-polyols is a promising approach for biomass valorization, but achieving selective conversion is challenging. In this study, we demonstrate a selective photocatalytic process to convert bio-polyols into formic acid (FA) or carbon monoxide (CO) by controlling the phase of TiO2. Through the phase control, high selectivity of FA or CO can be achieved from a wide range of bio-polyols. The phase-dependent selectivity is attributed to the difference in the adsorption configuration of FA. This work provides new insights for the design of photocatalytic systems for biomass conversion.