Carbon-based nanocomposites for sensing and catalysis

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Non-Technical Summary: Carbon-based electronic nanocomposites offer new opportunities to improve the environment by enabling sensors and improving processes that underpin the materials used in our day-to-day existence. Harnessing this potential requires deep understanding of the reactivity of these materials and new methods to create composite materials with novel functionalities. Chemists have a great understanding of the reactivity of small molecules in solution in a homogenous environment. With support from the Solid State and Materials Chemistry program in the Division of Materials Research and the Catalysis program in the Division of Chemistry, this research seeks to extend the known precision of small molecules to carbon-based nanomaterials, which have much more complex structures and solid-state organizations. Translating homogenous reactivity concepts for catalysis and sensing is accomplished by building on new methods for attaching structures to or assembling structures around carbon nanomaterials. For example, carbon-based nanomaterials can support metal catalysts when materials that actively bind the metals are part of the assembled compositions. Researchers at the Massachusetts Institute of Technology develop new methods that deliver electrons on demand to drive reactions in more efficient and selective processes. For example, in many cases in catalysis, rare metals such as platinum are needed. This is particularly true in catalysis needed for energy conversion technologies. This research creates supporting nanomaterials that allow for superior reactivity with much smaller quantities of these valuable materials. This effort also supports educational opportunities to diversify the STEM workforce through an exchange program between Massachusetts Institute of Technology and minority serving institutions, and to inspire new generations of scientists in both research and business careers. Technical Summary: With support from the Solid State and Materials Chemistry program in the Division of Materials Research and the Catalysis program in the Division of Chemistry, this research seeks to create multi-component functional materials systems from graphene, carbon nanotubes (CNTs), metal nanoparticles, and porous polymers. It leverages new methods for the covalent functionalization of graphene surfaces and confined cavities in porous polymers to produce highly active small ( 5 nm diameter) metal nanoparticles of controlled composition. Covalent modification of the sidewalls of carbon nanotubes is used as a method to “hard wire” molecular catalytic species to a conductive element and produce high catalytic activity and this approach will be expanded to the generation of asymmetric electrocatalysis. The electrophilic metal-oxo intermediates generated in the oxygen evolution reaction is used to react with alkenes for electrochemical epoxidation and chiral CNT-catalysts are employed to generate optically active epoxides. The researchers covalently functionalize carbon nanotubes and carbon nanotubes coated with porous poly(phenylene ether)s (PAEs) that contain metal binding ligands, which allows them to investigate reductive coupling of aryl-halides by Ni(0) in such conducting supports. Developing new synthetic methods for PAE opens up the scope of possibilities and a diversity of metal binding ligands can be included in the polymer. The principal investigator and his team also study whether porous ligands containing PAEs could be used to deliver only a single metal center to each NP with the balance of the composition containing one or more other earth abundant metals. Multi-elemental NP compositions are explored to create catalysts for fuel cell relevant reactions, including ethanol oxidation, hydrogen oxidation, and oxygen reduction as well as new chemiresistive sensors. Porous PAEs with integrated dyes are investigated as photoredox catalytic systems, in particular to determine if asymmetric PAE pockets can produce chiral products. In addition to advancing fundamental materials chemistry and potentially producing new commercially relevant technologies, this research also supports educational opportunities to diversify the workforce and inspire new generations of scientists in both research and business careers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.