Homogeneous Lewis and Brensted acids are respectively used to catalyze the reactions, which renders the process environmentally unfriendly, and causes corrosion problems of reactor systems [8]. To overcome these problems, a number of studies have been devoted to the development of heterogeneous acid catalysts for converting glucose into HMF, such as cation exchange resins, metal oxides, metal phosphates, zeolites, and carbon-based materials [1; 4; 7]. Niobium (Nb)-based catalysts are a class of metal oxides, which exhibit a strong acidic character, high chemical and thermal stability, and good performance in the HMF synthesis [9]. The Nb\({}^{5+}\) ions serve as Lewis acid centers responsible for the glucose-fructose isomerization, while the fructose dehydration is mainly catalyzed by Nb-OH species with Bronsted acidity [10]. In addition, niobium oxides (Nb\({}_{2}\)O\({}_{5}\)) have been identified as solid acids with excellent water-resistant properties [11; 12]. Various materials, such as beta zeolite [6], mesoporous silica SBA-15 [13], and carbon [5], have been investigated as supports for Nb-based catalysts for glucose conversion into HMF in biphasic water- organic solvent systems. However, a low initial concentration of glucose feedstock (or a high catalyst loading level) and a substantial formation of humins limited the practical use of these catalysts. Recently, [PERSON] et al. [14] synthesized alumina (\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)) functionalized with alkyl groups a hydrophobic acid catalyst for HMF synthesis from fructose, while [PERSON] et al. [15] designed a series of hydrophobic silica nanoparticles for catalytic conversion of glucose into HMF. The effect of hydrophobic properties on retardation of HMF condensation to form humins was addressed. Mesoporous carbon/silica nanocomposites (MCS) have attracted considerable attention in the catalytic processes for conversion of biomass-derived carbohydrates into HMF and other renewable chemicals [16]. The mesostructured silica framework provides good textural properties and thermal stability, while the carbon moieties possess hydrophobic properties that could reduce the formation of humins [14]. In addition, the carbon surface is covered with oxygen-functional groups, such as hydroxyl (\(-\)OH) and carboxyl (\(-\)COOH), which improved the adsorption of substrate molecules and dispersion of active metal species on the catalyst surface [17; 18]. Conventionally, the MCS materials are prepared by infiltration of carbon precursors, such as glucose, furfuryl alcohol, phenol, and formaldehyde, into preformed mesoporous silica, followed by carbonization or hydrothermal treatment [17; 18]. Natural rubber (NR) is a renewable elastomer that can be extracted from the _Hevea brasiliensis_ tree [19]. It is mainly composed of poly(_cis_-1,4-isoprene), and fully biodegradable. Thailand is one of the world's leading producers of NR. Due to its chemical composition and hydrophobic nature, it has been used as a renewable source for preparation of polymer/silica nanocomposites with high mesoporosity for adsorption and catalysis [20; 21; 22; 23]. Recently, we successfully prepared the MCS materials with tunable textural and hydrophobic properties using hexagonal mesoporous silica (HMS) and NR as a mesostructured framework and carbon source, respectively [23], which found potential application as a drug carrier. In this work, we prepared a series of Nb-based catalysts using pure silica HMS and NR-derived MCS nanocomposite as supports. The obtained catalysts were characterized for their physicochemical properties using various techniques and then were applied to the glucose conversion into HMF in a biphasic solvent of aqueous sodium chloride solution and tetrahydrofuran. Effects of the support type, Nb loading amount, catalyst loading level, reaction temperature and time on the glucose conversion and the product's yield were investigated. Moreover, the catalyst recyclability was evaluated to realize the practical use of our developed catalysts.