(42f) Enhancing CO2 Separation Performance of Composite Membrane By Incorporation of Amino Acid-Functionalized Graphene Oxide

Composite membranes composed of polymer phase and filler phase have been extensively studied for energy-efficient gas separation, especially for CO₂ separation, gasoline desulfurization, and alcohol dehydration, etc. The multiphase characteristics of composite membranes provide more degree of freedom to manipulate multiple interactions, tailor multiscale structures and integrate multiple functionalities in comparison with unfilled membrane. As the basic unit of protein, amino acid molecules are important in biology for promotion CO₂ transport. The composite membranes are fabricated by incorporating amino acid-functionalized graphene oxide nanosheets into sulfonated poly (ether ether ketone) (SPEEK) polymer matrix. Graphene oxide (GO) nanosheets are functionalized with amino acids through a facile two-step method by using dopamine and cysteine in succession. CO₂ separation performance of the as-prepared membranes is evaluated for CO₂/CH₄ and CO₂/N₂ systems. GO nanosheets increase more tortuous paths for the larger molecules, enhancing diffusivity selectivity. Amino acid with the carboxylic acid groups and primary amine groups simultaneously enhances solubility selectivity and reactivity selectivity. Accordingly, CO₂ molecules can transport quickly with the enhanced selectivity. When the content is 8 wt %, the optimum separation performance is achieved with selectivities of 82 and 115 for CO₂/CH₄ and CO₂/N₂, respectively, and CO₂ permeability of 1247 Barrer, significantly surpassing the Robeson upper bound reported in 2008. Besides, the mechanical and thermal stabilities of the composite membranes are also improved compared with pristine SPEEK membrane.