Hybrid organic/inorganic nanocomposites comprised of nanocrystalline iron oxide at the metastable beta-phase and graphitic carbon nitride (g-C3N4) were prepared via a facile in-situ growth strategy embedded in a solid state process. The hybridized beta-Fe2O3/g-C3N4 nanomaterials were thoroughly characterized by a variety of techniques, including UV-vis absorption, nitrogen physisorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). Their photocatalytic activity was evaluated under both simulated solar light and pure visible light irradiation against the photodegradation of methyl orange (MO), rhodamine B (RhB) and phenol. The prepared beta-Fe2O3/g-C3N4 nanocomposites were proven durable and significantly more efficient than the single components. The beta-Fe2O3 content in the final material was tuned to optimize the photocatalytic performance, with particular attention to the activity under visible light. The enhanced photoactivity was attributed to a) the improved optical properties of the prepared nanocomposites, presenting narrower band-gap energies and increased visible light absorption efficiency, and b) to the efficient separation of the photoinduced charge carriers driven by the matched band edges in the heterostructure. The predominant active species responsible for the photodegradation activity were determined and a possible mechanism is proposed. (C) 2016 Elsevier B.V. All rights reserved.