Breakthrough in porous liquids for carbon capture and catalysis

Carbon dioxide (CO₂) emissions remain a pressing environmental challenge, underscoring the urgent need for innovative, energy-efficient solutions. In line with national and global commitments to climate action, advancing carbon capture and conversion technologies is mission-critical to sustainably reducing emissions and achieving a net-zero future. In this context, a recent study by Yuan-Biao Huang and co-workers has introduced a disruptive material—a prototypical covalent organic framework (COF)-based smart porous liquid (PL), COF-301-PL, that merges the benefits of solid COFs and liquid materials, enabling efficient CO₂ capture and heterogeneous catalysis [1].

COF-301-PL is prepared in two steps: (1) surface grafting of a three-dimensional microporous COF, COF-301, with positively charged polyethylene glycol (PEG) and an organosilane co-functionalized imidazolium salt (PEG-Im-Si(OCH₃)₃); and (2) liquefaction via anchoring of a negatively charged PEG-tailed sulfonate (PEGS) canopy through ion exchange (Fig. 1). This ensures that COF-301-PL retains high microporosity (for gases such as CO₂) while maintaining its fluidity. What makes COF-301-PL exceptional is its liquid-like properties and ‘breathing effect’, meaning its excellent mass transfer capability in the liquid phase, alongside the dynamic expansion and contraction of its pores in response to CO₂ pressure. This feature enhances CO₂ storage, accelerates mass transfer, and optimizes catalytic efficiency, making it superior to traditional solid adsorbents under identical conditions.

Figure 1.

Schematic synthesis of the porous COF liquid COF-301-PL. NPs, nanoparticles.

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Thanks to its strong CO₂ capture ability, COF-301-PL serves as a gas reservoir for excellent CO₂ conversion in the presence of the catalyst tetrabutylammonium bromide. It dramatically improves the transformation of CO₂ and epoxide molecules into valuable cyclic carbonates, used in manufacturing plastics and pharmaceuticals. Compared to its solid COF counterpart and PEGS alone, COF-301-PL demonstrates 17-fold and 24-fold increases in catalytic efficiency, respectively. This advantage arises from COF-301-PL’s ability to store CO₂ at high pressure and gradually release it, acting as a self-sustaining micro-reservoir for catalytic reactions. This eliminates the need for continuous CO₂ supply, making industrial processes more efficient and energy-saving.

In essence, the development of COF-301-PL marks a milestone in porous liquid research. Its ability to reversibly adjust its pore structure to environmental conditions offers vast potential for improving industrial CO₂ capture, chemical synthesis, and gas separation technologies. Future advances in this area could enable the porous liquids’ translation into large-scale commercial adoption. By combining structural flexibility with high adsorption and catalytic performance, COF-301-PL exemplifies how the disruptive material design of combining fluidity and porosity can profoundly impact the challenge of carbon capture and utilisation (CCU) [2].

FUNDING

S.M. thanks Research Ireland grant 21/PATH-S/9454, and SSPC Reward funding, AzAds.

Conflict of interest statement. None declared.

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