Enhanced aqueous photocatalytic selective oxidation of HMF using simulated sunlight: Comparison of the performance of different photocatalysts

Selective conversion of biomass derivatives to high values added (HVA) compounds is an effective and sustainable route to fulfil the industrial request of chemicals. In this paper the partial oxidation of the lignocellulose derivative 5-hydroxymethyl-2-furfural (HMF) to high value compounds in green conditions has been investigated by using various photocatalysts and irradiation sources. In particular, TiO 2 based and alternative photocatalysts (Bi 2 O 3 , Cu 2 O, C 3 N 4 , ZnIn 2 S 4 ) were chosen with the aim of not only increasing the activity but also the selectivity in the partial oxidation of HMF. Bare ZnIn 2 S 4 , prepared in a simple way, showed to be the best photocatalyst under simulated sunlight illumination with conversion of HMF and selectivity towards 2,5-diformylfuran equal to 43 % and 68 %, respectively. Electrochemical measurements and experimental runs in the presence of various scavengers (tert-butanol, AgNO 3 , benzoquinone, Na 2 C 2 O 4 ) revealed that e − and O 2 − radicals play a key role in the selective conversion of HMF. A kinetic study was performed, and some kinetic parameters were determined by using the Langmuir-Hinshelwood model. • The partial oxidation of HMF to high value compounds has been studied under green conditions. • Different TiO 2 based and alternative TiO 2 photocatalysts and irradiation sources were investigated. • ZnIn 2 S 4 synthesized by using thiourea instead of carcinogen thioacetamide showed the highest photocatalytic activity. • High values of HMF conversion and FDC selectivity were achieved under simulated solar light irradiation. • Electrochemical and mechanistic investigations revealed the dominant role of e − and O 2 − radicals.