Compressed CO2 Accelerated the Synthesis of Mesoporous Heteroatom-Substituted Aluminophosphates for Enhanced Catalytic Activity



AFI-structured zeolites of aluminophosphates AlPO-5 and heteroatom-substituted aluminophosphates MeAPO-5 (Me = Fe, Co) have been synthesized in the presence of compressed CO2, the synthesized materials exhibiting mesoporosity without the use of additional mesotemplates. The mesoporosity was introduced by CO2-in-water emulsions acting as mesotemplate during the crystallization of the zeolites. In addition, the crystallization time was shortened in compressed CO2 compared with the conventional synthesis in the absence of CO2. The synthesized aluminophosphates MeAPO-5 (Me = Fe, Co) displayed much higher activities in the oxidation of styrene than conventional aluminophosphates MeAPO-5 (Me = Fe, Co) due to the presence of mesopores in the former catalysts, which favor the diffusion of reactants and products. The compressed CO2 method provides a simple, green, and economic route to hierarchical zeolites, which are of great importance for industrial applications.