Azobenzene/AlPO4-5 hybrid composites: synthesis, non-ambient stability and organization of the photoactive molecules

The regular pore systems of nanometric openings exhibited by zeolite frameworks make these porous materials ideal host matrices for achieving supramolecular organization of photoactive species, leading to versatile building blocks for the realization of hierarchically organized multifunctional composite materials[1]. Organic/inorganic hybrid materials (like zeolites+colorants) are currently used in strategic areas, from sustainable energy technologies to biomedical sciences. In these systems, photoactive molecules are organized in one-dimensional nanostructures inside the zeolite channels[2]. The zeolites with AFI topology have been extensively studied with the aim to produce new hybrid materials with optical properties. These studies [3] demonstrated the incorporation and the linear alignment of dyes into AlPO4-5, new spectroscopic properties were observed and the results indicated laser action in the system with properties tunable over a wide range. However for these systems, detailed information on the crystal structure and on the host/guest interactions are completely lacking. Here we present the results of a work aimed to the synthesis and the structural characterization of azobenzene/AlPO4-5 organic/inorganic hybrid composites, performed following these experimental steps: 1) synthesis of AlPO4-5 zeolite; 2) study of the thermal stability of the host zeolite by high temperature in situ synchrotron X-ray powder diffraction (ID22, ESRF, Grenoble); 3) preparation of the azobenzene/AlPO4-5 hybrid composites and their thermogravimetric analysis; 4) structural characterization of the dye guest molecule organization inside the zeolite pores by synchrotron X-ray powder diffraction (Xpress, Elettra, Trieste) [1] G. Calzaferri, Langmuir 2012, 28, 6216. [2] L. Gigli, R. Arletti, G. Tabacchi, E. Fois, J. G. Vitillo, G. Martra, G. Agostini, S. Quartieri, G. Vezzalini. J. Phys. Chem. C, 2014, 118, 15732. [3] Z. Lei, A. Vaidyalingam, P.K. Dutta J. Phys. Chem. B 1998, 102, 8557.