Size and Shape Exclusion in 2D Silicon Dioxide Membranes

Abstract

2D membranes such as artificially perforated graphene are deemed to bring great advantages for molecular separation. However, there is a lack of structure‐property correlations in graphene membranes as neither the atomic configurations nor the number of introduced sub‐nanometer defects are known precisely. Recently, bilayer silica has emerged as an inherent 2D membrane with an unprecedentedly high areal density of well‐defined pores. Mass transfer experiments with free‐standing SiO2 bilayers demonstrated a strong preference for condensable fluids over inert species, and the measured membrane selectivity revealed a key role of intermolecular forces in ångstrom‐scale openings. In this study, vapor permeation measurements are combined with quantitative adsorption experiments and density functional theory (DFT) calculations to get insights into the mechanism of surface‐mediated transport in vitreous 2D silicon dioxide. The membranes are shown to exhibit molecular sieving performance when exposed to vaporous methanol, ethanol, isopropanol, and tert‐butanol. The results are normalized to the coverage of physisorbed molecules and agree well with the calculated energy barriers.

PECVD and PEALD on polymer substrates (part II): Understanding and tuning of barrier and membrane properties of thin films

“…In our previous studies, we show that 2D silicates fabricated by ALD, thermal annealing, and transfer can deliver promising membrane activities for vaporized solvents such as methanol, ethanol, or isopropanol and gases such as $${\text{CO}}_{2}$$, $${{\rm{O}}}_{2}$$, $${{\rm{N}}}_{2}$$, and noble gases. [ 147,148 ] In the future, this field will be developed further and might become highly interesting for the fabrication of gas‐separation membranes with selectivity and permeabilities exceeding the current limitations for classical polymeric membrane systems.…”

“…Besides the VPI of polymers, new studies of our group also indicate that 2D silicate structures fabricated by ALD and strong annealing can be used as membranes for solvent vapor separation. [ 120,121 ] More detailed studies about the functionalization of potential membrane materials by VPI and ALD are planned in the future (see Section 6 at the end of this work).…”