(488x) Particle Surface Modification by Coating Ultra-Thin Microporous/Mesorporous Films

Porous thin films/coatings have wide applications in separations, corrosion protective coatings, gas storage, controlled drug delivery, and catalyst encapsulation for controlling reaction selectivity and maintaining catalytic activity. Ultra-thin microporous/mesorporous films/coatings are especially important for some applications. Inorganic films/coatings with few defects, such as zeolite membranes and mesorporous films, have been prepared by hydrothermal synthesis and sol-gel method. While these films/coatings have well defined uniform porous structures, it is difficult to control their thickness with the precision of angstroms. In order to create a porous structure, organic templates must be removed generally by calcination at high temperature. In this paper, we demonstrate a general method to create porous inorganic films/coatings with precisely controlled thickness down to several angstroms from dense organic/inorganic hybrid aluminum alkoxide (alucone) films grown by molecular layer deposition (MLD). The organic constituents in the film can be removed either by mild water etching at room temperature, or calcination in air at elevated temperatures. Because of the layer by layer growth process for MLD, the deposited polymer films have regular structure and the oxidation of MLD polymer films produces uniform interconnected highly porous structures with high surface area. The porous structure has both micropores and mesorpores with BET surface area as high as 1452 m2/g. We expect this porous thin film/coating growth technique, which offers both precise control of the thickness down to several angstroms and well defined porous structure, to have wide applications in catalyst functionalization, controlled drug delivery and nano-filtration.