Magnetically recoverable solid acid photocatalyst activated by white LED for sustainable high-yield synthesis of 5-ethoxymethylfurfural from biomass

The transition toward renewable energy demands innovative pathways for upgrading biomass into high-value biofuels with minimal environmental impact. Among various biofuel candidates, 5-ethoxymethylfurfural (EMF) has emerged as a superior green fuel additive due to its high energy density, low volatility, and compatibility with existing fuel infrastructure. However, achieving high yields from renewable carbohydrate sources remains challenging, particularly under environmentally benign conditions. Herein, we present a magnetically recoverable solid acid photocatalyst, Fe₃O₄@TiO₂-diamine-SO₃H, engineered through TiO₂ coating of Fe₃O₄ nanoparticles followed by covalent immobilization of 1,4-butanesultone via 3,5-diaminobenzoic acid. This tailored nanoarchitecture synergistically integrates firm Brønsted acidity, visible-light photocatalytic activity, and magnetic separability, enabling efficient etherification of HMF with ethanol and direct one-pot dehydration etherification of sugars under white LED illumination. The optimized process (100 °C, 1.5 h) delivered remarkable EMF yields of 97% from 5-hydroxymethylfurfural (HMF), 79% from fructose, and 65% from inulin in ethanolic solvent without any additional co-solvent. This approach offers several key advantages: (i) operational simplicity and minimal synthetic steps, (ii) use of abundant, inexpensive raw materials, (iii) mild, energy-efficient reaction conditions, and (iv) excellent catalyst reusability over six cycles with negligible activity loss. By uniting green solvent systems, visible-light activation, and magnetically assisted recovery, this work provides a scalable and sustainable platform for biomass-to-biofuel conversion. The exceptional performance and recyclability of Fe₃O₄@TiO₂-diamine-SO₃H underscore its strong potential for industrial application in next-generation renewable fuel production.