Synthesis and Characterization of Silica Membranes Prepared by Pyridine-Catalyzed Atomic Layer Deposition

Abstract

A novel method for preparing silica membranes with controlled pore size and porosity is reported. Mesoporous silica membranes were modified at near room temperature, using catalyzed atomic layer deposition (C-ALD) of silicon dioxide within the membrane. The catalyst, pyridine, in addition to reducing the reaction temperature, acted as a template for controlling pore size. The catalyst limited the deposition reaction within the mesoporous matrix, by reactant exclusion from the pores. This self-limiting pore size reduction was confirmed using single-gas permeation measurements on the modified membranes. The self-limiting pore size reduction was found extremely beneficial for reducing defects which contributed to viscous flow in the mesoporous membrane, without plugging up the membrane and maintaining reasonable fluxes. A mesoporous membrane with a N2 permeance of 3.5 × 10-7 mol·m-2·s-1·Pa-1, 3.3% of the flux of which was attributed to viscous flow, had its viscous flow reduced to less than 1% with a modest ...