Transition metal ion-modulated holey graphene oxide/hydrogel lamellar membranes for exceptional CO2/CH4 selectivity

Holey graphene oxide nanosheets enables uniform hydrogel filling in lamellar membranes • Metal ions densify gel network to increase selectivity and facilitate CO 2 transport • Zn 2+ balances CO 2 adsorption and desorption for rapid transport • Optimized membranes achieve CO 2 permeance of 27 GPU and CO 2 /CH 4 selectivity of 142 • The metal-ion regulation strategy demonstrates general applicability Exploiting efficient CO 2 /CH 4 separation membranes has emerged as indispensable platform for natural gas upgrading. Two-dimensional lamellar membranes offer immense opportunities in boosting CO 2 /CH 4 separation performance by introducing polar groups as facilitated transport carriers capable of forming strong interactions with CO 2 . Nevertheless, these lamellar membranes are largely restricted by inferior CO 2 /CH 4 selectivity of below 100, owing to the lack of efficient facilitated transport carriers to distinguish comparable kinetic diameter and polarizability of two gases. Herein, we bypass conventional carriers and discover a powerful and universal transition metal ion-modulated strategy to formulate holey graphene oxide/hydrogel lamellar membranes, rendering exceptional CO 2 /CH 4 selectivity over previously-reported lamellar membranes. In our strategy, transition metal ions play dual functions: performing high-efficient and tailorable CO 2 carriers via π-complexation for sustaining rapid permeance; and densifying hydrogel network within nanochannels via coordination for improving selectivity. By regulating the type and concentration of transition metal ions, our lamellar membranes yield a considerable CO 2 permeance of 27 GPU and a superior CO 2 /CH 4 selectivity of 142, which is about 3.7-folds of that without transition metal ions. This approach is broadly applicable to various metal ions, offering a paradigm shift in exploiting new lamellar membranes towards specific gas separation and beyond. Download: Download high-res image (187KB) Download: Download full-size image