Controlled organosilica networks via metal doping for improved dehydration membranes with layered hybrid structures

A layered hybrid membrane consisting of an organosilica top layer on a polymeric nanoporous substrate was successfully fabricated using bis(triethoxysilyl)ethane (BTESE)-derived organosilica sols doped with metal ions (Al and Zr). These membranes were applied to the dehydration of aqueous alcohol solutions including methanol (MeOH), ethanol (EtOH) and isopropanol (IPA). Metal-doped BTESE sols and gels were characterized via dynamic light scattering analysis (DLS), Fourier Transform Infrared spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), the isotherms of N2 sorption, laser scanning confocal microscopy (LSM), and scanning electron microscopy (SEM). During the dehydration of an IPA solution at 105 °C, the separation factors for Al-BTESE- and Zr-BTESE-derived membranes reached 8,000 and 10,000, respectively, which exceeded the separation factor for undoped BTESE membranes and indicates that doping with metal ions improves the dehydration performance of layered-hybrid membranes. In addition, Zr-BTESE-derived membranes prepared via the rinse method showed water permeance of 1.8 × 10-6 mol m−2 s−1 Pa−1, which is sufficiently high and compares favorably to that of polymer substrates. These membranes also showed a separation factor that was higher than 10,000. Correlations among the permeance ratios for H2O/MeOH, H2O/EtOH, and H2O/IPA were successfully predicted using modified gas translation (mGT) and bimodal pore models.