Bimetallic doping of LaNi into BTESE-derived hybrid organosilica membranes for H₂ separation

Bimetallic lanthanum/nickel (La/Ni) species were incorporated into 1,2-bis(triethoxysilyl)ethane (BTESE)-derived organosilica membranes by a sol-gel route to simultaneously tune the sub-nanometer pore architecture, hydrogen affinity and hydrothermal stability. Both La and Ni are mainly dispersed as amorphous Si-O-La and Si-O-Ni linkages within the BTESE network rather than as phase-segregated La₂O₃, La(OH)₃ or NiO related specises. The preferrable sites of La and Ni are in one ring without ethylidene groups by simulation module. The La/Ni ratios were investigated to regulate the pore structure and affect gas transport behavior. La₁Ni₉-BTESE delivered the highest H₂ permeance of 1.89 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ at 250 °C with an H₂/N₂ selectivity of 36.6, whereas La₂Ni₈-BTESE achieved the highest H₂/N₂ selectivity of 58.9 with H₂ permeance of 3.65 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹. Temperature-dependent permeation and apparent activation-energy analysis reveal that La/Ni co-incorporation provides a favorable balance between H₂ transport and N₂ exclusion. Density functional theory calculations further identify a framework-bound LaNi-BTESE motif as the most plausible local structure, in which adjacent Si-O-Ni/Si-O-La sites promote localized H₂ polarization at the Ni-containing site while N₂ adsorption requires larger framework deformation. The membrane retained 98% of its initial H₂ and N₂ permeance after 120 h exposure to water vapor at 200 °C, demonstrating the potential of LaNi-BTESE membranes for medium-temperature hydrogen purification.