Metal-organic nanosheets: a programmable two-dimensional platform for multistep catalysis

Two-dimensional nanomaterials such as graphene hold enormous potential for use in advanced electronics, energy, separation and composite materials applications. However, the simple chemical composition of many of these materials (e.g. boron nitride, molybdenum disulfide and transition metal dichalcogenides) mean small changes in their composition can disrupt their two-dimensional structure making it difficult to optimise their chemical, electronic, optical and mechanical properties performance for use in many applications.

Metal-organic nanosheets (MONs) are an emerging class of graphene-like two-dimensional nanomaterials. MONs combine the diversity of organic compounds with the unique properties of metal ions in a modular way that allows their properties to be tuned systematically. They can be dispersed in solvents to create stable suspensions which exposes their surface functionalities allowing them to interact with molecules in solution. Their very high surface area, readily tunable chemistry and the ease with which they can be recovered from reaction solvents by centrifugation make MONs ideal candidates for use as catalysts. Moreover, the periodic array of functional groups presented on the surface of MONs creates new opportunities for spatially organising multiple active groups to work together to catalyse reactions.

During this research project we will develop MONs as a new platform for catalysis. We will create MONs that form stable suspensions in reaction solvents at high concentrations and that can be functionalised with multiple catalytic active sites at well-defined positions. This will enable the formation of sophisticated active sites to facilitate reactions taking place at lower temperatures, It will also allow "one pot" catalysis of multiple reaction steps reducing the waste generated in purifying the compounds. The development of MONs as a new platform for catalysis will therefore enable the synthesis of new products in a more environmentally sustainable manner.

Knowledge- MONs have only recently emerged as a distinct class of two-dimensional metal-organic materials and therefore represent a distinct gap in the materials research market with enormous potential for academic and commercial importance. Key new technologies and knowledge that arise directly from this proposal include: increased UK expertise in the design, synthesis and characterisation of two-dimensional metal-organic materials; development of the chemistry required to post-synthetically functionalise MONs with a wide range of functional groups; a new generation of MONs able to form concentrated suspensions in target solvents; a new materials platform with the capability for spatial organisation of multiple catalytically active groups on a surface in order to create complex active sites and enable multistep catalytic pathways. This work will therefore contribute to the development of several important areas of the EPSRC's portfolio including: nanotechnology, synthetic coordination chemistry and functional materials.

Economy and Society- Graphene and other two-dimensional materials have received international recognition and billions of pounds in investment from research councils and industry. The success of other metal-organic materials such as frameworks, cages, gels and polymers demonstrate the potential for this class of materials. Catalysis is central to the UK's chemical industry, which generates in excess of £50 billion per annum according to the EPSRC's Catalysis Hub website. This proposal sits at the interface of these areas and will take advantage of the high surface area of 2D materials and tunability of MONs to bring known catalysts together in new ways.

Being able to undertake multiple reaction steps on a single, easy to recycle platform brings economic and environmental benefits by reducing the amount of solvents wasted during reaction work-up. The ability to pre-organise multiple components in well-defined ways, with spatial control, on a surface will enable the creation of complex, synergistic active sites leading to lower activation barriers and increased control over reaction products. Here, our focus is on demonstrating proof of principle for the use of MONs in this way and will focus on previously reported and well understood model systems taken from the literature. In the longer term, the sophisticated new catalysts developed could be used to enable the synthesis of new pharmaceutical compounds or facilitate reactions that utilise CO2 in line with UK priorities.

Catalysis was chosen as an application because I believe it has the highest potential for near-term economic and environmental impact. However, the core technology developed during this proposal, the ability to accurately position multiple active components in well-defined ways on a surface has the potential for enabling MONs to be exploited as a platform for use in diverse range of other applications. For examples, MONs could be used as a platform for creating sensors for detecting biomedically important macromolecules such as proteins allowing for the early diagnosis of disease in line with Industry Challenge Strategy Fund Priorities.
People- The PDRA involved in the project will have chance to gain expertise in the design, synthesis, characterisation and application of an emerging new class of supramolecular nanomaterials. MONs are complex, hierarchical materials and the PDRA will receive training in a diverse range of techniques in order to be able to determine the molecular and nanoscopic structure of the nanosheets. They will also develop skills in the synthesis of new ligands and MONs and their post-synthetic functionalisation and in monitoring complex multistep catalysts. The PDRA will have the chance to make a significant contribution in the fields of supramolecular chemistry, nanomaterials and catalysis making them well placed to pursue either an academic or industrial career path.