MgF2-Based Organized Porous Inorganic Nanofluorides as Heterogeneous Catalysts for Fluorination of 2-Chloropyridine

Abstract

The successful preparation of organized porous inorganic fluorides (OPIFs) with a high specific surface area is demonstrated for MgF 2. For the first time, macroporous MgF 2 OPIFs with a surface area of above 200 m 2 g −1 and mesoporous MgF 2 powder were prepared through the assembly of preformed MgF 2 nanoparticles and homemade polymer templates with a tunable size. These OPIF materials have been fully examined at different synthesis stages by means of powder X-ray diffraction, N 2 sorption, scanning electron microscopy, and transmission electron microscopy analyses and 19 F and 1 H solid-state nuclear magnetic resonance. The relation between the nature, the size, and the amount of polymer template on the porous structure was deeply investigated. The MgF 2 OPIFs present a higher thermal stability under air and F 2 calcination than MgF 2 NPs as the structuration of the OPIF composite considerably slows down the crystallite growth during thermal treatment under air. OPIF materials were evaluated for the first time as heterogeneous catalysts for the fluorination of 2-chloropyridine under HF gas as a fluorinating agent at 350°C. This study evidences catalytic sites with two Lewis acidity strengths (medium and low).