Catalytic Conversion of Cellulose to 5-Hydroxymethylfurfural: Advancements in Heterogeneous Catalysts and Cutting-Edge Hydrolysis Strategies

The catalytic conversion of lignocellulose-derived carbohydrates, particularly cellulose, into 5-hydroxymethylfurfural (HMF), holds significant potential as a crucial step in the sustainable production of valuable platform chemicals. This review presents the remarkable progress made in the field, with a specific emphasis on the role of heterogeneous catalysts, innovative methods for accelerating cellulose hydrolysis, and the design of flow reactor technologies. The distinctive properties and surface functionalities of catalysts facilitate the efficient breakdown of cellulose's intricate structure, thereby promoting selective hydrolysis leading to HMF formation. Therefore, this review comprehensively examines various categories of heterogeneous catalysts, including metal oxides/phosphates, zeolites, functionalized silica/carbon-based materials, heteropolyacids (HPAs), and metal-organic frameworks (MOFs), highlighting their unique mechanisms and performance in cellulose conversion. Furthermore, the review describes the intriguing progress in hydrolysis strategies (pretreatment techniques and advanced heating systems) that have been crucially involved in overcoming the challenges associated with cellulose recalcitrance and achieving enhanced HMF yields. The synergistic interactions between catalysts and innovative hydrolysis methods have played a central role in the breakthroughs within cellulose conversion technology. Another aspect covered in this work is the advancement in using fixed-/fluidized-bed reactors and slug microreactors for the continuous production of HMF. Lastly, the current challenges and future perspectives are presented to propose the dilemma and development direction for efficient cellulose-to-HMF conversion. © 2023 Wiley-VCH GmbH.