Decarbonisation Technology May 2025 Issue

using metal ions and organic ligands. Certain MOFs have other advantageous properties for carbon capture applications, including high thermal and chemical stabilities, tuneable selectivity, low energy of desorption, and recyclability. MOF-based carbon capture has the potential to deliver significant advantages over incumbent technologies, including increased energy efficiency, lower process complexity, and smaller operating footprints. Figure 2 shows MUF-16 (MUF = Massey University Framework), a MOF discovered at Massey University, New Zealand, in 2018. The conclusions from de-risking work and a survey of the commercial landscape indicated that the adsorbent is at the forefront of CO₂ capture from various gas emission streams. Captivate Technology was subsequently launched as a start-up in 2023. MUF-16 is made inexpensively and easily in large quantities using a straightforward process and readily available raw materials. It is then pelletised and deployed in adsorbent columns. Industrial flue gases or biogas are separated into CO₂-rich and CO₂-light streams using vacuum pressure swing adsorption (VPSA). Its network of pores traps CO₂ via weak interactions, and CO₂ is easily removed once the MUF-16 bed reaches saturation capacity. This regenerates MUF-16 for another round of carbon capture, a process that can be repeated many thousands of times. The rate of CO₂ adsorption is high for the adsorbent which means there are no kinetic limitations on its performance. Captivate Technology has developed the use of MUF-16 for separating CO₂, determining its performance in real-world scenarios, and scaling up to pilot demonstration at industrial sites across New Zealand. De-risking showed that the combination of selectivity, capacity, tolerance to water and impurities, ease of manufacture, and cost make it an ideal adsorbent for CO₂ capture from flue gas streams. The US Department of Energy targets for purity (95%) and recovery (90%) can be exceeded using a simple step VPSA process, with high productivity and low energy consumption. Solid-state adsorbent technology for carbon capture requires one-quarter to one-

Adsorbed CO

Figure 2 MUF-16 crystalline structure and pellets

for the CO₂ fraction of the emissions stream and thermal energy is not used to regenerate the adsorbent. Such low-cost methods are not just achieving emission reductions; they are spurring a completely new CO₂ feedstock utilisation opportunity as low-cost CO₂ is produced at scale. From being a harmful waste greenhouse gas, new opportunities for harnessing CO₂ are rapidly emerging, and as a consequence an emerging market for CO₂ use is also rapidly growing, for example, in the manufacture of liquid fuels or polymers. Captivate is an integral part of the emerging circular economy for carbon that obviates the need for the introduction of extra carbon into the biosphere from fossil fuel extraction. CO₂ is captured in waste emission streams and transformed into useful products using established and emerging process technologies, for example, with the addition of hydrogen produced from renewable electricity. As shown in Figure 1 , once combusted or used, the CO₂ is captured and transformed again into a useful product, allowing the circular use of CO₂. Captivate Technology has built a carbon capture capability by developing a porous, solid-state material that is a sponge for CO₂. This novel material, a type of metal-organic framework (MOF), selectively sieves CO₂ from gas streams. The process is continuous and recyclable, generating a steady stream of gaseous CO₂ to be stored or used. The company is rapidly moving to demonstration scale in collaboration with industrial partners and end users. MOFs are porous, crystalline materials built