Why we invested: Promethean Particles, with Dr Marina Fuentes
Combining my passion for climate tech with impactful innovation.
I’ve always been passionate about climate tech and sustainability. My journey into environmental awareness started at a young age when my mother, who herself grew up immersed in nature in the Cantabrian countryside, gifted me the book “The Wounded Earth” by Miguel Delibes de Castro, a renowned Spanish environmentalist and author. I vividly remember the physical pain I felt when I saw the images depicting the damage caused by climate change and human activity. From that moment, I knew this was something I couldn’t ignore.
Since joining Mercia Ventures, I’ve been fortunate enough to work in sectors I truly care about. Our team is split across strategic sectors, which allows each of us to focus on the technologies we’re most passionate about. You can feel the excitement in the room when one of us brings a deal for discussion. There’s a real joy in knowing that we’re investing not only in companies with strong potential for returns, but also in technologies that can drive meaningful change. This is what led me to Promethean Particles.
The technology, the team, the opportunity
Before I encountered Promethean, I had been developing an investment thesis around carbon capture—a critical technology for achieving net zero emissions. Even with large-scale deployment of renewables like solar and wind, many industries—such as heavy manufacturing, cement, steel production and energy generation—continue to produce significant amounts of carbon dioxide (CO₂) that are difficult to eliminate. Carbon capture and storage (CCS) is essential for reducing emissions in these sectors, where decarbonisation remains a challenge.
During this work, I spoke with numerous players in the carbon capture space and came to understand the key technological bottlenecks that still exist.
The technology: A breakthrough in Metal-Organic Frameworks (MOFs)
Promethean specialises in the production of metal-organic frameworks (MOFs), a fascinating class of materials with immense potential. MOFs are highly porous, giving them an enormous surface area—one gram can cover an entire football field. This unique property makes them ideal for capturing small molecules like CO₂, hydrogen and water, making them a game-changer in industries like carbon capture, biogas upgrading and water harvesting.
One of the most exciting aspects of MOFs is their versatility. Scientists have already developed more than 100,000 different MOF structures, each tailored to specific applications. This staggering variety demonstrates how adaptable MOFs are in solving complex industrial and environmental challenges. While carbon capture is what sparked my interest initially , I quickly saw that Promethean’s MOFs have potential far beyond this. For example, they are transforming biogas purification by turning raw biogas into high-purity biomethane, a cost-effective solution for the energy sector, particularly as subsidies for biogas decrease in Europe.
Overcoming historical barriers
Despite their potential, MOFs have historically been held back by high production costs and scalability challenges. Promethean has overcome these barriers with its continuous-flow manufacturing reactors, which enable MOFs to be produced quickly (in minutes instead of hours) and at a fraction of the cost compared to traditional methods. With a reactor production rate of 1,000 tonnes per year, we believe Promethean already has the largest potential to manufacture MOFs globally.
The continuous flow reactor also solves other long-standing issues with batch production, such as inconsistent quality output, high energy consumption and limited scalability. Promethean’s ability to ensure consistent particle size and substantially more efficient production has unlocked the door to widespread adoption of MOFs, particularly in carbon capture and biogas purification—two sectors that are vital in the fight against climate change.
The team: Proven leadership and vision
Of course, technology is only part of the story. One of the major reasons we invested in Promethean is the strength of their team, led by James Stephenson, the CEO. James brings a wealth of experience in chemical manufacturing and has a clear vision for Promethean’s future. Having a capable and passionate team is as important as the technology itself when it comes to driving a company like Promethean forward.
The Opportunity: Scaling for Global Impact
Promethean is at a pivotal stage. The £8m investment led by Mercia Ventures and Aramco Ventures, completed in August 2024, will enable the company to expand its manufacturing capacity, grow its team, and further demonstrate the wide-ranging potential of MOFs across various industries. We believe that Promethean’s ability to manufacture MOFs at a scale and cost-effectiveness previously unseen will unlock previously uneconomic market applications for the technology across carbon capture, energy storage, and biogas. The combination of this with the track record of the CEO James and the strength of the rest of the team made this investment decision a clear yes for us.
A full-circle moment
On a personal note, investing in Promethean felt like a full-circle moment for me. By serendipity, I did my PhD at Nottingham, and it was Ed Lester, Promethean’s CSO, who gave the Welcome to University speech to my PhD cohort. Now, years later, I have the opportunity to support his groundbreaking work. It’s a reminder of how connections and experiences can come together in unexpected and impactful ways.
If you share my passion for climate tech and want to learn more about Promethean’s groundbreaking work, feel free to reach out or visit their website. This is an exciting journey, and we’re proud to be part of it. You can read more about the investment here.