Carbonic anhydrase-embedded ZIF-8 membrane reactor with improved the recycling and stability for efficient CO capture.

Carbonic anhydrase (CA) enzyme-based absorption technology for CO capture has been intensively investigated. However, low solubility of CO and poor stability of CA severely limits its industrial utilization. Here, hydrolyzed polyacrylonitrile (PAN) membrane (HPAN) was first modified by polyethyleneimine (PEI) with a large number of amino groups, which has a strong affinity for CO. Then, ZIF-8 was grown in situ on the surface of HPAN/PEI membrane by using the metal chelation of PEI and Zn. In this process, CA was embedded inside ZIF-8 by co-precipitation (CA@HPAN/PEI/ZIF-8). The resultant CA@HPAN/PEI/ZIF-8 exhibited high catalytic activity for CO capture compared with free CA, which was due to the synergistic enhancement of CO capture by PEI and ZIF-8 with high affinity to CO and enzymatic catalysis. The yield of CaCO by CA@HPAN/PEI/ZIF-8 in the process of one-time conversion of CO was 13.6-fold higher than free CA. Furthermore, the CA@HPAN/PEI/ZIF-8 showed better thermal stability, storage and reusability than free CA. Free CA retained only 18.3 % of its original activity after 18 days of storage, whereas CA@HPAN/PEI/ZIF-8 remained 48.7 % of its original activity. The total CaCO yield by CA@HPAN/PEI/ZIF-8 was 74.9-fold that of free CA after 8 consecutive rounds of CO conversion.