Construction of a Hollow SiO<sub>2</sub>-Based Porous Liquid Based on Polydopamine and Its Application in CO<sub>2</sub> Separation of Membranes
Ping Gao, Shuhao An, Yu-Shu Han, Changjun Peng, Jun Hu, Honglai Liu
Abstract
Considering that polydopamine (PDA) formed by self-polymerization of dopamine can easily and firmly adhere to solid surfaces, in this work, a PDA-coated modified SiO2 material HS@PDA was first obtained by mixing dopamine with hollow SiO2 (HS), and then the pH of the solution was adjusted to protonate PDA on the surface of the material. Then, the protonated HS@PDA was mixed with large-sized polyethylene glycol sulfonate (PEGS) ionic liquids, and the silicon-based porous liquid HS@PDA@PEGS was synthesized through electrostatic interactions. Furthermore, HS@PDA@PEGS was added to the polymer Pebax-1657 as a filler to prepare several mixed matrix membranes (MMMs), and the CO2/N2 separation performance of the prepared MMMs was evaluated. The results show that the filler HS@PDA@PEGS has good interfacial compatibility with the polymer matrix, which can effectively solve the agglomeration problem of solid particles in MMMs. When the loading of HS@PDA@PEGS in the MMMs was 20 wt %, the CO2 permeability increased from 50.3 to 144.2 Barrer, whereas the CO2/N2 selectivity increased from 33.5 to 65.5, that is, its CO2 permeability and CO2/N2 selectivity increased by 186.6 and 95.5%, respectively. When only 20 wt % PEGS was added to the Pebax membrane, the CO2 permeability and CO2/N2 selectivity of the MMMs only increased by 63 and 16.4%, respectively. When the same amount of HS (1 wt %) was added to the Pebax membrane, although the CO2 permeability of the MMMs can be increased by 155.5%, CO2/N2 selectivity was increased only by 27.6%. These results demonstrate that porous liquid-doped MMMs benefit from the respective advantages of ionic liquids and solid pores and that the introduction of dopamine also provides a simple preparation strategy for the liquefaction of solid porous materials.