Chem
Volume 6, Issue 11, 5 November 2020, Pages 3038-3053
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Article
Selectivity Control in Photocatalytic Valorization of Biomass-Derived Platform Compounds by Surface Engineering of Titanium Oxide

https://doi.org/10.1016/j.chempr.2020.08.014Get rights and content
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Highlights

  • Selectivity for the reduction of bioplatforms depends on exposed facets of TiO2

  • Coupling products as fuel precursors are produced in high yields

  • Surface-oxygen vacancies play pivotal roles in controlling the selectivity

  • Density of oxygen vacancies governs electronic structure of adsorbed species

The Bigger Picture

Photocatalysis has emerged as a useful approach to the sustainable production of value-added products from biomass, in which selectivity is the key issue because a number of transformations are possible when multifunctional biochemicals are the reactants. As one of the most popular photocatalysts, TiO2 has mainly been applied to reactions like pollutant degradation that concern more about activity than selectivity. The knowledge about selectivity-controlling principles for TiO2 is limited. Here, we report the first illustration of TiO2-based photocatalysis that succeeds in modulating product selectivity in bioplatform transformations. Fine chemicals or jet-fuel precursors have been produced in high yields by controlling the density of oxygen vacancies on TiO2, which governs surface adsorption and reaction and thus determines the product selectivity. This work offers useful insights into the design of selective photocatalysts for biomass valorization by surface engineering.

Summary

Photocatalysis has offered a promising opportunity for selective transformation of biomass to high-value chemicals or fuels under mild conditions. Whereas titanium oxide has been widely used for photocatalytic pollutant degradation, H2 evolution, and CO2 reduction, few studies have been devoted to TiO2-based photocatalytic valorization of biomass or biomass-derived platform compounds. Here, we report on surface-controlled photocatalysis of TiO2 for selective valorization of furfurals and vanillin that are lignocellulose-derived key platform compounds. The reaction can be switched from hydrogenation of aldehyde group to C–C coupling by manipulating exposed facets; furanic and aromatic alcohols or coupling products, which are fine chemicals or jet-fuel precursors, could be produced with high selectivity. Our studies elucidate that the facet-dependent density of oxygen vacancies governs the charge distribution and adsorption strength of surface species and thus controls product selectivity. The present work offers an example of selectivity control by engineering TiO2 surfaces for valorization of biomass-derived feedstocks.

UN Sustainable Development Goals

SDG7: Affordable and clean energy
SDG11: Sustainable cities and communities

Keywords

biomass-derived platforms
photocatalysis
selectivity control
surface engineering
titanium oxide

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2

These authors contributed equally

3

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