Hybrid SrZrO3-MOF heterostructure: surface assembly and photocatalytic performance for hydrogen evolution and degradation of indigo carmine dye

In this work, we developed a novel heterostructure based on the coupling of a metal organic framework (MOF LEEL-037) with an inorganic semiconductor (SrZrO3) for two photocatalytic applications: hydrogen evolution from water splitting and the degradation of indigo carmine dye. A complete study of the structural, morphological, textural, optical, electronic, and electrochemical properties of MOF, SrZrO3 and the heterostructure is presented through X-ray diffraction, scanning electron microscopy, UV-Vis diffuse reflectance spectroscopy (UV-Vis), photoluminescence spectroscopy and electrochemical impedance spectroscopy, evaluating the effect of these parameters on the catalytic performance of the materials. The heterostructure formation was studied by transmission electron microscopy, varying the loading of LEEL-037 from 0.5 to 5%. Microscope images corroborate the effective dispersion of LEEL-037 and the appropriate contact between the metal organic framework and SrZrO3 particles. It was found that the photocatalytic activity of SrZrO3 under UV light was significantly enhanced with the incorporation of MOF LEEL-037, which enhances the charge separation and transport, leading to an improved photocatalytic performance. After 1 h of reaction, the heterostructure with the optimal amount of LEEL-037 (5%) exhibited a hydrogen evolution of 66.9 A mu mol, corresponding to 6 times the activity of pure SrZrO3 (11.2 A mu mol). LEEL-037 exhibited an activity of 34.1 A mu mol, but the rate of hydrogen production was not constant. The stability and efficiency of the charge transference in the bare semiconductors and the heterostructure were studied through photoluminescence and electrochemical analysis, which demonstrated the suitable band coupling between SrZrO3 with MOF LEEL-037, the enhanced charge separation and injection from one semiconductor to another, and the reduction in the recombination of the electron-hole pairs. These studies and the integral correlation of the properties of the materials allowed to establish the path of the photogenerated charges and to propose the photocatalytic mechanisms involved in the reactions. The photocatalysts were also evaluated for the degradation of indigo carmine, where the highest dye degradation (69%) was exhibited by the heterostructure. Based on our results, we propose the use of the heterostructure SrZrO3-5% MOF LEEL-037, obtained by an easy and low cost method, as a suitable new photocatalytic material for environmental and energy applications, highlighting at the same time the promising properties of metal-organic frameworks for their coupling with a variety of inorganic semiconductors.