Catalytic effect of trifluoroacetic acid on the CO2 transport properties of organic-inorganic hybrid silica membranes

Developing silica membranes that are highly selective for CO2 has always been a challenge due to the small sizes of the pores and less amount of CO2 philic sites in a typical silica network structure. Herein, we describe the fabrication of silica (tetraethoxysilane) membranes functionalized with 3-aminopropyltriethoxysilyl (APTES) and trifluoroacetic acid (TFA). An interaction generated among primary (NH2) amines and TFA was identified, which was then also revealed by the reversible nature of CO2 adsorption/desorption - an opposite trend from observations when using another catalyst (HCl). The resultant TEOS-APTES (TFA) membranes demonstrated CO2 permeance of 3.8 x 10 - 7 mol m - 2 s - 1 Pa- 1 and CO2/N2 selectivity of 35 at 50 0C via the effect of surface diffusion. This is attributed to the increased microporosity and structural variations affected by TFA, which enhanced molecular sieving and controls the CO2-philic sites (-NHCOCF3) via interaction with amines. This novel approach would be effective for the energy-efficient fabrication of highly CO2-permeable membranes.

Automated summary

This study presents a novel approach for the fabrication of highly CO2-permeable membranes by functionalizing tetraethoxysilane (TEOS) membranes with 3-aminopropyltriethoxysilyl (APTES) and trifluoroacetic acid (TFA). The interaction between APTES and TFA enables reversible CO2 adsorption/desorption, leading to increased microporosity and structural variations that enhance molecular sieving and control the CO2-philic sites. This method shows great potential for energy-efficient membrane fabrication.