Ionic liquid-decorated melamine–terephthalaldehyde framework as an efficient metal-free nano-catalyst for fructose dehydration into 5-hydroxymethylfurfural

Abstract

An efficient nano-catalyst based on melamine–terephthalaldehyde framework with ionic liquid functionality (MTF-IL) was synthesized through the post-synthetic modification of organic linkers with 1-methylimidazolium bromide. This MTF-IL was investigated for its efficacy as a metal-free nano-catalyst in fructose dehydration to synthesize 5-hydroxymethylfurfural (HMF). Optimization via Response Surface Methodology (RSM) identified optimal reaction conditions of 21 wt% catalyst, 100 °C, and 50 min, resulting in a remarkable HMF yield of 98 % in DMSO. Kinetic studies suggested that the dehydration process mediated by MTF-IL follows pseudo-first-order kinetics, exhibiting a low activation energy of 14 kJ. mol⁻¹ at optimal conditions. The nature of the anion pair in MTF-IL significantly influenced its catalytic activity, with enhanced performance corresponding to bromide. Additionally, MTF-IL demonstrated characteristics of a heterogeneous catalyst, facilitating straightforward recovery and reuse. This research underscores the potential of covalent organic framework-derived solid acid catalysts for the valorization of biomass carbohydrates.