Boosting the CO2 capture efficiency through aromatic bridged organosilica membranes

Abstract

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.