Water-compatible lanthanide-based Lewis acids for the efficient conversion of glucose and other carbohydrates to produce 5-hydroxymethylfurfural (HMF) were demonstrated in a biphasic reactor using sec-butyl phenol as the extracting solvent. The reaction of glucose dehydration to HMF was found to proceed under near-neutral conditions (pH = 5.5) and a moderately high yield of 42 mol % could be obtained. The combined catalytic system also showed effectiveness to convert other polysaccharides to HMF. Furthermore, the aqueous phase was recycled and used for multiple times without significant loss of catalytic performance.