The new efficient heterogeneous catalysts on the basis of modified polymer carbon nitrides are developed for the conversion of hexose carbohydrates to 5-hydroxymethylfurfural (HMF)the most important basic compounds for the modern chemical industry. Carbon nitride was modified by interaction with HCl, PCl 5 and CrCl 3 . The structure and composition of the modified carbon nitrides have been studied by IR spectroscopy and X-ray diffraction analysis. Established, that propounded catalysts provide the selective conversion of hexose carbohydrates into 5-hydroxymethylfurfural with a minimum yield of humic compounds under mild conditions.