Mixed matrix membranes comprising dual-facilitated bio-inspired filler for enhancing CO2 separation

Abstract

• A dual-facilitated biomimetic zeolitic imidazolate framework (Bio-ZIF) was designed. • Biomimetic active sites and amino groups played dual-facilitated functions in MMMs. • Dual-facilitated functions facilitated quickly CO 2 transport in MMMs. • The resulting MMMs exhibit superior CO 2 /CH 4 separation performance. In this work, a novel dual-facilitated bio-inspired zeolitic imidazolate framework (Bio-ZIF) was proposed to simulate the structure and function of carbonic anhydrase (CA), because it can overcome the low stability and high price of the CA. A novel type of mixed matrix membrane (MMM)-composed of Bio-ZIF and Pebax® MH 1657 (Pebax) was fabricated and used to enhance CO 2 separation performance. The bio-inspired active sites of Bio-ZIF can catalyze the reversible hydration of CO 2 in the form of bicarbonate to facilitate the quick transport of CO 2 across the MMMs, increasing CO 2 permeability. Furthermore, the amino groups of Bio-ZIF reacted with CO 2 to produce zwitterion as an intermediate during the reversible reaction, facilitating CO 2 permeation in the MMMs. It can be concluded that Bio-ZIF performed the dual-facilitated functions in the MMMs by reversible hydration and reversible reaction with CO 2 molecules. Thus, the as-prepared MMMs exhibited an excellent CO 2 separation performance. Particularly, Pebax/Bio-ZIF-12 MMM presented an optimal CO 2 permselectivity with CO 2 permeability of 542 ± 6.0 Barrer and CO 2 /CH 4 separation factor of 40 ± 0.4, surpassing the 2008 upper bound. This work provided an ingenious strategy to design bio-inspired fillers to achieve dual-facilitated functions in MMMs for enhancing CO 2 separation.