Calcination of a gallium-N-phenylene-N hybrid copolymer under an argon atmosphere gave nano-sized gallium nitride-carbon cluster composite material. ESR spectral examinations of the calcined materials reveals the possibility of an electron transfer in the process of gallium nitride -> carbon clusters with an oxidation site at gallium nitride particles and a reduction site at carbon clusters. The calcined material was found to reduce methylene blue under visible light irradiation. (c) 2007 Elsevier Ltd. All rights reserved.