Characterisation and rational design of porous conjugated polymers for solar energy conversion

Conjugated microporous polymers (CMPs) have exciting applications as sensors, emitting diodes but also as potential materials for transforming solar energy to either electricity for direct use or to chemical fuels such as hydrogen for energy storage, the chemical fuel could be transformed to electricity in a later stage. I propose to concentrate on these last two applications that have the potential to accelerate the energetic transition to "low-carbon" energies due to the possible high availability and low costs of those materials.

CMPs are formed of building blocks ("bricks") that are assembled into complex 3D skeletons that form nanoparticles ("houses"). These "houses" will have different shapes and depending on the shape, be more or less functional. The "houses" can in turn interact and assemble into a "city". In the same way as "houses" can present larger or smaller volumes and "cities" can be more or less dense, CMPs can have a broad distribution of pore sizes. Ultimately, the way "houses" are organised and connected will impact transport and efficiency of the "city". Similarly, CMPs 3D skeleton and pore network will impact photo-electrochemical properties and device efficiency.

The chemical design of the elemental "bricks" is almost infinite and thus, their combinations impossible to screen by trial and error method. Furthermore, synthesizing some combinations might be a real challenge or even impossible. Therefore, chemical intuition is what ultimately guides synthetic chemists. However, even in state-of-the-art labs, synthesizing new CMPs, and then characterizing them is a slow process. In this fellowship, I propose to develop a computational screening tool that can be used complementary to combinatorial chemistry to speed up materials discovery. Reaching the prediction stage within the time of the fellowship would be over-optimistic but defining a set of new design rules to guide synthesis of new CMPs can be achieved. The computational tool will aim to link chemical design with electronic properties of the material.

All the structural properties of CMPs have to be grasped by the computational tool. In order to answer the challenge, different computational techniques will have to be combined in a multiscale modelling scheme where parameters for the larger scale model are extracted from the shorter scale model Such models must be experimentally validated to be useful for calculating photo-electrochemical properties. CMPs are built in a random manner and possess no long-range order. Thus, structural characterization is challenging. Part of the project is therefore dedicated to the validation of the model by a combination of spectroscopic techniques.

CMPs are so far insoluble and thus processing them into thin film is challenging. Thin films would be ideal for the applications I want to investigate and would further enable optical and electrical characterization. I propose to further investigate processing routes to thin films from this insoluble CMPs as well as using my computational tool to propose new chemical design for soluble CMPs.

Computational screening can help accelerate the technological advancement of materials design, more specifically for solar energy conversion. Solar energy conversion can provide a response to the global technological challenge of finding low carbon power generating solutions. This fellowship builds on the UK pioneering work in conjugated microporous polymers (CMPs). Conjugated microporous polymers inserted in devices to convert solar energy in either electricity or chemical fuel as hydrogen have the potential to combine low environmental impact, high throughput processing and low cost unlike photoactive materials used in existing technologies. These advantages could contribute to an acceleration of carbon savings as well as an acceleration of the worldwide energy transition due to availability and possible low cost. As such, we believe that this fellowship can help to address a major global societal challenge.

Computational screening of small molecules is already used for drug discovery for example but computational screening of macromolecules present further challenges especially due to complex hierarchical microstructures. Because of the increasing computational resources, computational screening of macromolecules such as CMPs is likely to play an increasing role in the future for various applications based on smart polymers e.g. for engineering bio-compatible polymers. Therefore, incorporating structural modelling of macromolecules in computational screening tool has potential impact in various academic fields such as porous polymers and materials, soft matter, hierarchical systems, synthetic biology, plastic electronics, polymer electrolytes for energy storage. Computational screening of macromolecular systems has therefore potential medium and long-term commercial outcomes. As a consequence, this fellowship will reinforce UK leadership in advanced materials and has the potential to reinforce UK industrial competitiveness.

Part of the fellowship will be dedicated to the creation of an educational online game and outreach events, to promote science especially within the young community, make people participate to materials discovery and to raise awareness and promote more generally low-carbon energy to the public.