Síntese e caracterização de polímeros de coordenação modificados com nanopartículas metálicas

Abstract

Coordination polymers are compounds formed by one or more polycationic ligands (connectors) coordinated to metal cations (nodes) forming one-, two- or three-dimensional coordination entities. In this context, metallorganic networks, better known as MOFs, are a special class of coordination polymers because they present a structure with well-defined porous dimensions. Metalorganic networks present interesting properties such as high crystallinity, high porosity and good thermal stability. One of the areas that has grown the most in recent years is the use of metallic nanoparticles to modify coordination polymers, in particular, metallic nanostructures such as gold, silver and copper that stand out due to their plasmonic properties. This type of modification can promote changes in the properties of the compounds, such as optical properties, for example. In particular, the intensification of Raman bands due to the surface-enhanced Raman scattering effect. In the present work the coordination polymers HKUST-1 (short for Hong Kong University of Science and Technology) and JR-172 were modified with two different types of gold nanoparticles synthesized with sodium borohydride and synthesized with sodium citrate. In the first case sodium borohydride results in tetrahydroxyborate as the stabilizer of AuNPs and in the other case sodium citrate which also the surface protector resulted in the formation of citrate ions on the surface of the nanoparticles. The modifications were carried out during the synthesis of the coordination polymers (in situ modification) and after the preparation (post-synthesis modification). Different characterization techniques were used to observe the changes in the properties of the coordination polymers, and changes in the properties of these materials were observed after modification with gold nanoparticles.