Growing Carbon Chains on Organometallic Networks

Lead Research Organisation: Imperial College London
Department Name: Chemistry

Abstract

The chemistry of carbon monoxide (CO) and carbon dioxide (CO2) is deeply embedded in our future plans for energy production, chemical manufacturing and sustainable living. Remediation of CO2 has become a major topic of research in the last ten years and conversion of CO to hydrocarbons is already being applied on vast scales in industry. Catalysis underpins the development of this industry. COx-to-fuels, COx-to-molecules and COx-to-materials (x = 1 or 2) research is indispensable for the growth of the economy, improvement of quality of life, and regulation of gas emissions that contribute to climate change.

Arguably the most established technology operating in this landscape if Fischer-Tropsch (F-T) catalysis. The F-T process converts mixtures of CO and H2 into short to medium chain hydrocarbons. Recent research has focused on the use of CO2 rich gas streams. This reaction can be considered as a controlled polymerisation and hydrogenation of CO / CO2 to generate liquid fuels. Despite its advantages, F-T catalysis produces simple alkanes and alkenes, not complicated molecules. Carbon chain formation occurs alongside removal of the oxygen atoms, in the form of H2O, reducing complexity and value. F-T does not capitalise on the potential chemical intricacy that could be introduced when combining COx units to form chains.

In this project we will develop an entirely new approach to use CO and CO2 in chemical manufacture. We plan to exploit a remarkable recent finding from our labs (JACS, 2018, 13614): that carbon chains of 3 to 4 units of length can be grown from CO and CO2 on organometallic networks. We will develop underpinning science to discover the rules for chain growth. We will deliver new approaches to generate small carbon chains from CO and CO2 with control of size and shape. The new carbon chains will be exploited in synthesis as the major molecular component in the construction of complex organic molecules.

The long-term vision behind this project is the development of a modern approach in catalysis that is complementary to both F-T processes and CO2-to-materials research. One that builds molecular complexity from CO and CO2. This proposal describes a three-year project that represents the first steps from discovery toward this goal.

Planned Impact

In the coming century the renewable sector has the potential to supplant the current chemical industry and allow society to break away from environmentally damaging resources. Key to the development of this industry will be effective ways to add value to CO2 or CO available as renewables. The pathway to impact begins in academia and flows through industrial engagement to industrial application and ultimately to the public.

The initial impact from this project will be based in academia. I have a track-record of influence in the academic sector. To date in my independent career, I have found new ways to re-use environmentally persistent fluorocarbons and developed new catalysts that exploit the cooperative behaviour of two or more metals in close proximity. My work has found a deep and lasting impact in UK science and beyond. For example, in 2017 my work was recognised with the Harrison-Meldola Prize - the most prestigious early career award from the Royal Society of Chemistry. In 2018, aspects of my research were highlighted in both Science and Chemistry World. There is no reason to believe that the output from this project will be any less influential.

In the long term, the findings can be expected to impact the chemistry industry. Chemical manufacture processes of relevance include the production of polymers, the manufacture of agrochemicals, pharmaceuticals and fine-chemicals. The realisation of just one new route from CO2 or CO to a commercially relevant molecule or material would lead to a tangible economic impact for this project. Engagement with industry will occur through networks at Imperial such as the Pharmacat Consortium, Manufacturing Futures Lab, Energy Futures Lab, Agri-net and the Sustainable Gas Institute. Industrial impact will be further realised through participation in Eli Lily's open innovation programme. Public engagement will be achieved through outreach activities such as the Imperial College Festival.
 
Description In this project we are investigating new chemical reactions that couple together molecules of carbon monoxide (CO) and hydrogen (H2) to form carbon chains (JACS 2018, 13614). This work is important as this type of controlled polymerisation, hydrogenation and dehydration of CO is a method to form fuels and starting materials for fine chemical synthesis. It is operated on large scales by industrial processes that employ heterogeneous catalysis which incorporate transition metal active sites. The approach has genuine green credentials as it is possible, in part, to replace CO with CO2 as a chemical feedstock, or indeed use CO / H2 mixtures generated from renewable sources (biogas).

We have developed a series of homogeneous systems that have the potential to model the active sites of catalysis and shed new light on how carbon chains are grown from combining CO and H2 on metal ions. We have shown that C2, C3 and C4 chains can be grown from CO by controlling the reaction and that both the rate and selectivity of this chain growth process is highly dependent on the transition metal fragment employed (Chem. Sci. 2021, 14845). Furthermore, we have demonstrated that both ends of the newly formed carbon chain are potentially reactive, allowing methods for chain elongation with chemical reagents other than CO (aldehydes, ketones, isonitriles). We have also shown that it is possible to hydrogenate these species, displacing them from the transition metal and allowing a stepwise process to make C3 and C4 oxygenates (carbon chains containing C, H and O atoms) from CO and H2 (Angew. Chem. Int. Ed. 2022, DOI:202202241).

In separate work we have shown that transition metal carbonyl and main group hydrides can combine to generate formyl complexes. While these are often unstable trapping them between two metals (e.g. Cr and Mg) allows their isolation and complete characterisation. We have shown that in certain cases metal formyl complexes are competent intermediates in the formation of ethenediolate, C2, chains. We have recently summarised the mechanistic role of formyl intermediates in carbon chain growth from CO and hydrides and published a review article on this topic. In unpublished work, we have shown that bis(formyl) complexes can be isolated, and for the first time structurally characterised. Despite being invoked as intermediate in carbon chain production, as yet we see no evidence for carbon-carbon bond formation from bis(formyl) complexes we have prepared.

We are currently 3 year into this 3-year grant and continue to work toward the aims of the project, we are continuing to develop systems that are catalytic in at least one of the metals involved in forming carbon chains.
Exploitation Route The long-term vision of our project is to develop understanding that will lead to realisation of new homogeneous catalysts that combine CO and H2 selectively to make hydrocarbon or oxygenate chains. This grand challenge would provide a complementary approach to established industrial methods (Fischer-Tropsch catalysis), that while efficient do not allow precise control over selectivity. One can imagine that if such an approach can be realised that homogeneous catalysts could be used to precisely control the length, shape and molecular content (C/O ratio) of carbon chains made by these methods. This in turn would open up new possibilities in chemical manufacturing with sustainable feedstocks.
Sectors Chemicals,Environment,Manufacturing, including Industrial Biotechology
URL http://crimmingroup.org
 
Description Johnson Matthey (JM) 
Organisation Johnson Matthey
Country United Kingdom 
Sector Private 
PI Contribution Two way exchange of knowledge: JM where included as project partners in the Growing Carbon Chains on Organometallic Networks project. We have contributed to bilateral discussions and knowledge sharing with JM during regular project update meetings.
Collaborator Contribution JM have contributed to bilateral discussions and knowledge sharing with Imperial during regular update meetings. They have supported the group with an in-kind donation of precious metals used specifically in this project.
Impact There are no outputs associated with the collaboration rather it is focused on knowledge sharing.
Start Year 2018
 
Description Catalysis Workshop and Video 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact We have conducted a workshop on catalysis monsters locally in London. This is an outreach project in which participants are taught about the fundamentals of catalysis and why it is important. They can make their own 'catalyst monster' (for example with strong-arms or laser eyes) to make and break bonds. We have run this at the invention rooms in White City London and at the science museum London. As part of this workshop we commissioned and designed a video describing catalysis to 10-12 years. This video is now available on youtube: https://www.youtube.com/watch?v=iZNSRfWqg9Q and is promoted through the Imperial College Channel.
Year(s) Of Engagement Activity 2021
URL https://www.youtube.com/watch?v=iZNSRfWqg9Q