Boosting the CO2 capture efficiency through aromatic bridged organosilica membranes

CO₂ capture have attracted much attention due to serious environmental problems caused by excessive CO₂ emission. Membrane-based technologies boasting of energy-saving and high-efficiency advantages exhibit much prospect in treating this issue. Benefited from excellent molecular sieving properties and high porosity, a wide variety of organosilica membranes were applied to the CO₂ separation process. Nevertheless, most studies focused on the development of linear alkanes bridged organosilica membranes. Few researchers were dedicated to developing organosilica membranes with aromatic groups. In fact, the aromatic groups (e.g., such as benzene groups) functionalized organosilica precursors can endow derived membranes with robust network structures. Moreover, aromatic benzene groups can provide infinite possibilities of decoration. Herein, organosilica membranes fabricated using phenyltriethoxysilane (PhTES) with pendant benzene group, bis(triethoxysilyl)benzene (BTESB) with bridged benzene group and 4,4′-bis(triethoxysilyl)-1,1′-biphenyl (BTESBPh) with bridged biphenyl group, were used for CO₂ capture separation. The effect of the location of aromatic benzene groups (bridged or pendant type) and the number of aromatic bridges (single benzene and biphenyl bridges) were evaluated in detail. For CO₂/N₂ mixtures separation at 50 °C, PhTES membranes displayed a CO₂ permeance of 1087 GPU (1GPU = 3.348 ✕ 10⁻¹⁰ mol m⁻² s⁻¹ Pa⁻¹) and CO₂/N₂ selectivity of 30. In contrast, BTESB membranes maintained a similar level of CO₂/N₂ selectivity of 34 but approximately 2.5 times enhanced CO₂ permeance of 2600 GPU. BTESBPh membranes featured an unprecedentedly high CO₂ permeance of 5465 GPU and CO₂/N₂ selectivity of 13. This clearly indicated that the aromatic functionalized organosilica membranes presented great potential in CO₂ capture applications. Furthermore, the gas permeation properties of organosilica membranes can be finely tuned via the change of the location and the number of the benzene groups.