A simple hydrothermal approach was adopted for the construction of novel porous Cd-3(C(3)N(3)s(3))(2)/CdS composites that were endowed with heterojunctions. In the synthesis, Cd-3(C3N3S3)(2) (denoted as Cd-3(TMT)(2)) was adopted as precursor, and a spontaneous self-decomposition process is responsible for the formation of heterojunctions and porous structure. By controlling the hydrothermal temperature and hence the level of Cd-3(TMT)(2) decomposition, the photocatalytic activity of the Cd-3(TMT)(2)/CdS composites can be regulated. The composite prepared at 155 degrees C exhibits outstanding photocatalytic performance towards toluene selective oxidation to benzaldehyde, giving a benzaldehyde formation rate of 787 mu mol g(-1) h(-1) under visible light (lambda >= 420 nm) without the need of any solvent. The excellent performance is ascribed to the unique Cd-3(TMT)(2)/CdS porous structure: large in surface area and rich in heterojunctions. In photocatalysis, the large surface area of a catalyst enables enrichment of adsorbed reactants, and the presence of heterojunctions facilitates separation and transfer of photogenerated electrons and holes. It is envisaged that the method is suitable for the generation of organic/inorganic composites for photocatalytic purposes.