Selective photocatalytic C–C coupling of isopropanol into pinacol with concurrent hydrogen evolution over GONaOH photocatalyst

Abstract

If a sacrificial agent is selectively oxidized to generate high-value chemicals during photocatalytic hydrogen production, then photocatalytic water splitting is more meaningful in consideration of green chemistry. GO_NaOH was obtained after hydrothermal treatment of graphene oxide (GO) using 10 mol L⁻¹ NaOH. The average hydrogen production rate could reach 7.36 mmol h⁻¹ over 0.50 g L⁻¹ GO_NaOH photocatalyst for a reaction of 12 h. And the sacrificial agent isopropanol could undergo selective oxidative C–C coupling to generate pinacol. The isopropanol conversion rate was 77.95%, and the pinacol selectivity was 62.32%. Also, the GO_NaOH photocatalytic selective oxidative C–C coupling mechanism of isopropanol was further studied. The ˙OH concentration on the photocatalyst surface was verified as a key factor influencing pinacol selectivity. Under the effect of GO_NaOH photocatalyst, ˙OH radicals were used for the oxidative dehydrogenation of isopropanol to generate 2-hydroxyisopropyl radicals, and pinacol was generated through C–C coupling. Meanwhile, acetone byproducts could further undergo hydrogenation–dehydrogenation coupling reaction with isopropanol to finally generate pinacol.