An effective, template-free synthesis methodology has been developed for preparing mesoporous nitrogen-doped SrTiO 3 (meso-STON) using glycine as both a nitrogen source and a mesopore creator. The N-doping, large surface area and developed porosity endow meso-STON with excellent activity in visible-light-responsive photodegradation of organic dyes.The exceptional electro-optical properties and physicochemical stability of the perovskite SrTiO 3 (STO) give rise to its attractive performance in photocatalytic applications of solar power, including photocatalytic degradation of organic pollutants, water splitting and photoreduction of CO 2 .1-3 However, the intrinsic large bandgap energy (E g = 3.2 eV) of SrTiO 3 allows only the utilization of UV light, encompassing approximately 5.0% energy of the sunlight. 4 A variety of transition metals (TM) have been doped into a STO's crystal matrix in efforts to tune its electronic bandgap for harvesting visible light.
5,6Unfortunately, TM-doping can also bring about either phase impurity or fast recombination of photogenerated charge carriers. Nonmetal-doping represents another effective strategy to realize visible-light response.7-9 Indeed, it was found that N-doped SrTiO 3 (SrTiO 3Àx N x , STON) exhibited excellent photoreactivity and stability under visible-light irradiation.
10Mesoporous-structured photocatalysts are highly desirable in photocatalysis since their large specific surface area (SSA) and mesoporous channels greatly facilitate adsorption, diffusion and surface reaction of the reactants.11 STO perovskite belongs to the cubic crystal system, and typically has low SSA and poor porosity. Moreover, the porosity of STO could be further destroyed by the known processes of nitriding STO to STON.
5,12Although mesoporous STO has been prepared via templatedirected synthesis using various soft (e.g. surfactant or polymer 13 ) and hard (e.g. inorganic salts 14 ) templates, the synthesis of mesoporous STON has rarely been achieved.Here we report a novel, template-free synthesis methodology to prepare mesoporous STON using glycine as both a nitrogen source and a mesopore creator. Aqueous solution of glycine and Sr(NO 3 ) 2 was dropped into ethanol solution of titanium butoxide under stirring, followed by solvent evaporation and subsequent calcinations at 550 1C for 2 hours. The obtained STON was characterized by XRD, TEM, FTIR, UV-vis, and XPS techniques and used for the photodegradation of three refractory organic dyes under visible-light irradiation.Only a strong single peak appears in the small angle XRD pattern (Fig. 1) of the STON sample, suggesting that it possesses disordered wormlike mesopores. 15 The TEM image in Fig. 2A nicely confirms such mesoporosity. The HRTEM image inserted in Fig. 2A reveals that the walls of the mesopores are comprised of single crystal perovskite STON. The labelled lattice distances are consistent with those of (100) and (110) diffractions obtained from XRD tests (Fig. S1, ESIw). In contrast, the STO sample presents poor mesoporous featu...