Facile Synthesis of Halloysite Nanotubes-Supported Acidic Metal-Organic Frameworks with Tunable Acidity for Efficient Fructose Dehydration to 5-Hydroxymethylfurfural

In this work, a novel composite solid acid catalyst, i. e. PVP-HNTs@UiO-66-SO₃H−X (X=0.5, 1, 2, 3), was obtained in the first time. Polyvinylpyrrolidone (PVP) modified halloysite nanotubes (HNTs) was employed as the carrier for immobilizing acidic metal-organic frameworks (MOFs) of UiO-66-SO₃H−X, where X stands the amount of immobilized acidic MOFs. By simply varying the ratio of supporter and acidic MOFs, the acid functional sites of composite solid acid catalyst can be effectively adjusted. Then the obtained composite solid acid catalyst was well characterized and systematically investigated in the fructose to 5-hydroxymethylfurfural (HMF) transformation. Under the optimized reaction conditions, with the presence of PVP-HNTs@UiO-66-SO₃H-2, the 92.4% HMF yield was obtained. What's more, the PVP-HNTs@UiO-66-SO₃H-2 can be easily recycled at least five times without significant loss of activity.