class of materials with exciting chemical and structural properties. Well known for their ultra-high surface areas in excess of 7,000 m2 per gram, MOFs also have uniform pore structures, tuneable porosity, and significant flexibility in network topology and chemical functionality. The first permanently porous MOF was discovered in the late 1990s, and the term ‘metal-organic framework’ was coined. MOFs are highly porous crystalline frameworks comprised of multivalent metals bonded to multitopic organic linkers (see Figure 2 ). The choice of metal ion and organic linker molecules is almost limitless, and it is estimated that more than 100,000 MOFs have so far been synthesised. Despite significant promise, the development of MOFs has been mainly the purview of academia, with novelty rather than utility being the main driver. This has resulted in MOFs acquiring a reputation for high-cost and low industrial-scale manufacturability. Role of MOFs in energy-efficient CCS systems Along with their high porosities and incredibly high surface areas, certain MOFs also have other advantageous properties for carbon capture applications. These include high thermal and chemical stabilities, tuneable selectivity, low energy of desorption, and recyclability (Britt et al., 2009). MOF-based CCS has the potential to deliver significant advantages over incumbent technologies, including increased energy efficiency, lower process complexity, and smaller operating footprints. December 2022 represented a significant milestone for the technology. Promethean Particles and the University of Nottingham announced the completion of a MOF- based carbon capture pilot project at Drax‘s incubation facility in Selby, North Yorkshire. The aim of the project was to show how MOFs would perform outside of the laboratory and in relevant industrial conditions and, as such, demonstrate the achievement of technology readiness level (TRL) 5 (see Figure 3 ). The project was successful and not only showed that MOFs could capture the CO 2 from the flue gas, but also helped inform future process design. Rapid progress of the technology has since
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been demonstrated. Further pilots have been completed, including a more sophisticated, automated system that meets TRL6 criteria. This system can be transported to customer sites to provide in-situ demonstrations of the technology against the customer’s particular gas separation requirements. When not in use by customers, Promethean connects the system to its 1 megawatt (MW) gas-fired water boiler to help further inform process and application development activity. Figure 3 The technology readiness level scale (adapted by The Welding Institute [TWI]) Along with their high porosities and incredibly high surface areas, certain MOFs also have other advantageous properties for carbon capture applications The Department for Energy Security and Net Zero recently announced financial support for Promethean to develop a TRL7 system capable of capturing 1-3 tonnes per day of CO 2 as a winner of the government’s CCUS Innovation 2.0 competition. It is expected that these ever-increasingly sophisticated pilots will help de-risk this next-generation technological approach and lead to broader adoption of the technology across a range of point- source emitters in various industrial sectors. As highlighted in Figure 4 , the operation
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