Biocatalytic Membranes for Carbon Capture and Utilization

Abstract

Innovative carbon capture technologies that capture CO₂ from large point sources and directly from air are urgently needed to combat the climate crisis. Likewise, corresponding technologies are needed to convert this captured CO₂ into valuable chemical feedstocks and products that replace current fossil-based materials to close the loop in creating viable pathways for a renewable economy. Biocatalytic membranes that combine high reaction rates and enzyme selectivity with modularity, scalability, and membrane compactness show promise for both CO₂ capture and utilization. This review presents a systematic examination of technologies under development for CO₂ capture and utilization that employ both enzymes and membranes. CO₂ capture membranes are categorized by their mode of action as CO₂ separation membranes, including mixed matrix membranes (MMM) and liquid membranes (LM), or as CO₂ gas-liquid membrane contactors (GLMC). Because they selectively catalyze molecular reactions involving CO₂, the two main classes of enzymes used for enhancing membrane function are carbonic anhydrase (CA) and formate dehydrogenase (FDH). Small organic molecules designed to mimic CA enzyme active sites are also being developed. CO₂ conversion membranes are described according to membrane functionality, the location of enzymes relative to the membrane, which includes different immobilization strategies, and regeneration methods for cofactors. Parameters crucial for the performance of these hybrid systems are discussed with tabulated examples. Progress and challenges are discussed, and perspectives on future research directions are provided.

Keywords: CO2 capture; CO2 reduction; biocatalyst; carbonic anhydrase; enzyme; formate dehydrogenase; immobilization; membrane.

Figure 1

Categories of biocatalytic membranes used for CO₂ capture.

Figure 2

Functionalities of membranes used for biocatalytic CO₂ conversion.

Figure 3

Chemical structures of active sites of CA enzyme (shown in orange oval) and CA-mimics (shown in blue rectangles).

Figure 4

Modified graphitic carbon nitride decorated with a Cobalt complex for photocatalytic NADH regeneration (Reprinted with permission from Ref. [148]. Copyright 2020, American Chemical Society).