Designing and Fabricating Highly CO2-Selective Composite Membranes Inspired by Iron-Fortified Mussel Adhesive System

The industrial availability of gas separation membranes relies heavily on membrane permeance, permselectivity and stability, among which the polyether-containing copolymer membranes acquire a desirable balance. However, the condensability- governed separation limits their overall selectivity, which seriously restricts their efficient application in natural gas purification. In the present study, a facile method, inspired by mussel adhesive phenomenon, was developed to enhance the size-sieving ability of the polymer membranes. Dopamine and ferric ion were incorporated into the polymer solution of Pebax^® 1657, and the corresponding composite hollow fiber membrane was prepared through the conventional dip-coating method. Compared with the pristine Pebax membrane, the hybrid membranes exhibit significant increase in CO₂/CH₄ selectivity (from 22 to 75), owing to the increased chain rigidity arising from iron-induced dopamine oxidation and crosslinking. The size-sieving ability of the membranes can be tailored by simply tuning the iron/dopamine ratio. On the other hand, the CO₂ permeance remains rather high due to the well-controlled free volume properties. Such a bio-inspired method may pave a versatile way to the rational design of the size-selective membranes for diverse applications.