Functionalized metal–organic frameworks with strong acidity and hydrophobicity as an efficient catalyst for the production of 5-hydroxymethylfurfural

Abstract

Benzenesulfonic acid -functionalized MOF with hydrophobic network and high acid density is synthesized. • A benzenesulfonic acid-functionalized MOF is prepared. • The catalyst has a strong hydrophobic network and high acid density. • 98.0% yield of HMF is obtained in the dehydration of fructose. • The sulfonated metal–organic framework is stable for recycling. In the dehydration of fructose to 5-hydroxymethyl furfural (HMF), in situ produced water weakens the acid strength of the catalyst and causes the rehydration of HMF, causing unsatisfactory catalytic activity and selectivity. In this work, a class of benzenesulfonic acid-grafted metal–organic frameworks with strong acidity and hydrophobicity is obtained by the direct sulfonation method using 4-chlorobenzenesulfonic acid as sulfonating agent. The resultant MOFs have a specific surface area of greater than 250 m 2 ·g −1 , acid density above 1.0 mmol·g −1 , and water contact angle up to 129°. The hydrophobic MOF-PhSO 3 H exhibits both higher catalytic activity and selectivity than MOF-SO 3 H in the HMF synthesis due to its better hydrophobicity and olephilicity. Moreover, the catalyst has a high recycled stability. At last, fructose is completely converted, and 98.0% yield of HMF is obtained under 120 °C in a DMSO solvent system. The successful preparation of the hydrophobic acidic MOF provides a novel hydrophobic catalyst for the synthesis of HMF.