New platinum nanocomposites were synthesized using mesoporous carbon nitride as a stabilizing matrix and carrier for nanoparticles by the method of reduction of H 2 PtCl 6 •6H 2 O by methanol-water mixture. The textural, morphological, optical properties, structural and phase compositions of composites with different contents of loaded platinum particles were studied. The obtained composites have prospects for use as effective heterogeneous catalysts in chemical and photo,-electrochemical processes.