Efficient Conversion of Carbohydrates into 5-Hydroxymethylfurfural Using Graphitic Carbon Nitride Bearing Brönsted Acid Sites

The current focus in biomass conversion research is to achieve high yields and selectivity of 5-hydroxymethylfurfural (HMF) as a platform chemical from renewable sources, emphasizing the need for a sustainable and efficient heterogeneous acid catalyst. The goal is to develop a low-cost, energy-efficient approach that aligns with sustainability principles. In this work, graphitic carbon nitride bearing Brönsted acid sites (g-C3N4–SO3H) was synthesized and applied as a catalyst for converting carbohydrates into HMF in dimethyl sulfoxide (DMSO) as a solvent. The catalyst structure was determined using modern spectroscopic techniques such as Fourier-transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution X-ray photoelectron spectrometry (HRXPS), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET), and thermogravimetric analysis (TGA) evaluated the stability of the catalyst. In order to optimize the reaction efficiency, several factors were examined, such as the temperature, solvents, catalyst mass, and reaction time. These parameters were carefully studied and adjusted in order to optimize the reaction conditions. As a result, the reaction yield was highest at about 60% HMF after 3 h at 120 °C with g-C3N4–SO3H (30 mg) using fructose as the substrate. The combination of AlCl3 and g-C3N4–SO3H gave an excellent yield, which accounted for 58% of HMF from glucose at 3 h at 120 °C. Additionally, the catalyst employed in our study can be easily recovered and reused for subsequent reactions. Our research presents a straightforward and efficient procedure for synthesizing the catalyst, enabling the conversion of glucose or fructose into 5-hydroxymethylfurfural (HMF) with a high yield within a short reaction time.