(41a) Controlled Porosity and Structure In Nanoporous Metal Oxide Monoliths by Sacrificial Vapor Phase Infiltration of Polyesters

Preparation of porous metal oxide materials has attracted considerable attention because of  possible use in separations, catalyst support, chemical sensors, optical and electronic devices, energy storage and solar cells. Although many methods are known to  synthesize  porous materials, obtaining porous materials with well defined macro-scale morphology remains an important challenge. In the present work, we demonstrate that porous metal oxide materials (including Al₂O₃ and TiO₂) with controlled pore size and distribution are produced by sacrificial infiltration of polyesters with reactive metal organic precursors and water. Results were discovered during  recent experiments using atomic layer deposition (ALD) to treat and coat polymer materials.   We found that exposing polyesters to Al₂O₃ and TiO₂ ALD processes, using trimethyl aluminum and titanium tetrachloride precursors, respectively, produced organic-inorganic hybrid materials with a physical macro-structure that followed the original polymer template. After post annealing, nanoporous materials with pre-defined macro-structure were prepared. Nitrogen adsorption/desorption analysis confirmed that the surface area, pore volume, and pore size distribution were  tuned by the process parameters, such as temperature and vapor exposure time. The highest BET surface area of prepared porous Al₂O₃ and TiO₂ were  ~440m²/g and 210m²/g respectively. The infiltration mechanism and chemical reactions were explored by in-situ infrared transmission analysis and quartz crystal microgravimetry. Thermal properties and air stabilities of the hybrid materials were assessed by the DSC/TGA and Ex-situ IR experiments.