Imobilização do complexo cis-Ru(bpy)2Cl2 nas redes orgânicas covalentes RIO para o desenvolvimento de novos fotocatalisadores heterogêneos

Abstract

The use of light in chemical reactions, particularly in photocatalysis, has emerged as a sustainable and efficient approach for performing organic syntheses. Among the most promising photosensitizers are metal complexes such as [Ru(bpy)₃]²⁺, known for their ability to perform electron transfer processes upon visible light excitation. Although homogeneous systems offer advantages such as high diffusion in the reaction medium and well-defined active sites, their recovery and reuse pose challenges, especially for large-scale applications. A viable solution is the immobilization of these complexes onto solid supports, combining the benefits of both homogeneous and heterogeneous catalysis. In this context, covalent organic frameworks (COFs) stand out as excellent immobilization platforms due to their porous structures, high surface area, and thermal stability. Based on this, the present work proposes the immobilization of the cis-[Ru(bpy)₂Cl₂]·xH₂O complex onto COFs containing imine linkages with azo groups, aiming to develop more efficient and reusable heterogeneous photocatalysts for light-driven transformations. Four COFs were synthesized, named RIO-n (Reticular Innovative Organic Frameworks), and used as supports for the ruthenium complex, resulting in the formation of novel composites of the type [RuII(bpy)₂@RIO-XX]Cl. The materials were characterized by techniques such as Fourier-transform infrared spectroscopy (FT-IR) and powrder X-ray diffraction (PXRD). Inductively coupled plasma mass spectrometry (ICP-MS) revealed ruthenium content ranging from 0.20% to 0.46% by weight in the composites. The photocatalytic potential was evaluated using singlet oxygen probes and phosphorescence analyses. The results indicated that the composites are not effective photocatalysts for singlet oxygen-mediated reactions. On the other hand, they showed good performance in singleelectron transfer processes. Additionally, integrity tests revealed limitations in the use of these materials in acetonitrile due to leaching.