Surpassing Robeson Upper Limit for CO2/N2 Separation with Fluorinated Carbon Molecular Sieve Membranes

Abstract

The CO2-philic properties of powdered fluorinated triazine frameworks make them promising candidates for fabrication of porous CO2 separation membranes. This is rarely reported because of lack of suitable synthetic approaches. Here, fluorinated membranes based on covalent triazine frameworks are prepared through a rational design of aromatic nitrile monomers containing fluorine and ether groups via a sol-gel polymerization process. The CO2 separation performance rises significantly with the fluorine content in the membrane. With functionalized triazine units, fluorine, and ether groups, these carbon molecular sieve membranes obtained after pyrolysis exhibit intrinsic ultra-micropores, high surface areas and excellent thermal stability under air. Excellent CO2 permeability and CO2 to N2 selectivity surpassing the Robeson upper bound are achieved. Our general design and synthesis protocol allow an easy access to fluorinated porous membranes, thus significantly expanding the currently limited library of CO2-philic and chemically stable membranes for highly efficient CO2 separation.