Structurally tuning microwave absorption of core/shell structured CNT/polyaniline catalysts for energy efficient saccharide-HMF conversion

Microwave absorption and catalytic activity have been synergistically integrated into a core/shell structured CNT/polyaniline (PANI) hybrid catalyst that enables localized heating on the catalyst surface and uplifts energy efficiency in the dehydration reaction of saccharides to 5-hydroxymethylfurfural (HMF). Results reveal that the integration of CNT and polyaniline significantly improves the overall saccharide conversion and HMF yield. The PANI shell thickness and morphology are controlled by both reactant feeding ratio and polymerization reaction rate. A thinner and rougher PANI shell is favourable to enhance the overall microwave absorption, improve heat transfer efficiency to catalyst surface and thus reaction efficiency. The highest energy efficiency of 7.6 mmol kJ⁻¹ L⁻¹ is reached in 10 min with CNT/PANI catalyst (30 wt% CNTs) and 19 W input power. Moreover, the packing of polyaniline shell on CNT core facilitates its separation from reaction mixture and effectively prevents catalyst loss. These catalysts show excellent recyclability that the catalyst activity can be completely recovered by a simple re-doping process in 1.0 M sulfuric acid. This work opens up a new window in microwave responsive catalyst design that enhances energy efficiency in saccharide-HMF conversion reactions and promotes the economic feasibility of such reactions in practice.