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A series of organic–inorganic acidic hybrids in uniform nanospheres were prepared by self‐assembly of phosphotungstic acid (HPW) and pyridine (PY) or triethylamine (TEA) without using a template and surfactant. The prepared samples were characterized by XRD, TEM, FTIR, and N2 adsorption–desorption isotherms, and their surface acidity was determined by titration. Particularly, PY‐PW‐1 showed a predominant catalytic performance in the near complete etherification of 5‐hydromethylfurfural (HMF) to 5‐ethoxymethylfurfural (EMF) with a high yield of 90 % at 80 °C in 24 h, which might be ascribed to its relatively high acidity and smaller particle size. This kinetic study elucidated the superior activity of PY‐PW‐1 in the HMF‐to‐EMF conversion. Fructose could also be directly converted to EMF in a moderate yield of 55 % at an elevated temperature of 120 °C by a cascade reaction process. In addition, PY‐PW‐1 could be reused five times with no evident loss of its catalytic activity. Importantly, the downstream product of EMF (i.e., ethyl levulinate) in an excellent yield of 93 % could also be achieved from HMF by further increasing the reaction temperature to 140 °C.

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Biomass, as the most abundant and renewable organic carbon source, can be upgraded into various value-added platform molecules. To implement more sustainable and economic catalytic biomass valorization, reusable heterogeneous catalysts would be one of the preferable choices. In this work, a series of phosphotungstic acid-based solid hybrids were produced by assembly of phosphotungstic acid with different pyridines using a facile solvothermal method. The obtained 3- phenylpyridine-phosphotungstate hybrid displayed superior catalytic performance in the upgrade of fructose to methyl levulinate with 71.2% yield and 83.2% fructose conversion at 140 ºC for 8 h in methanol, a bio-based and environmentally friendly solvent, which was probably due to its relatively large pore size and high hydrophobicity. This low-cost and eco-friendly catalytic process could be simply operated in a single pot without cumbersome separation steps. In addition, the 3- phenylpyridine-phosphotungstate catalyst was able to be reused for four times with little deactivation.

A high yield of methyl levulinate (82.5%) was achieved from fructose via a one-pot multi-step conversion process using acidic 3-FPYPW as a heterogeneous catalyst.