Collaborative Research: Porous Molecules as a Platform for Solid-State Organometallic Chemistry

With the support of the Chemical Synthesis program in the Division of Chemistry, Eric Bloch of the University of Delaware and David Powers of Texas A&M University will study new methods for the preparation of porous catalysts. Porous materials are widely used around the world for a wide variety of applications, including water filtration and/or softening, as desiccants, and in medicine. A subset of porous materials is used on a large scale in catalytic applications, including in the cracking of hydrocarbons. A key challenge in using porous materials as catalysts, however, is controlling and optimizing their reactivity where total surface area, structure type, and stability can play a role in determining their activity. The Bloch/Powers team is building on promising preliminary results to develop a new method for the synthesis of active porous catalysts by creating reactive salts. In this method, a charged nonporous reactive organometallic species will be combined with an oppositely-charged porous non-reactive ion to afford a new class of porous solids. It is envisioned that for porous materials so constructed catalytic activity will be finely tunable across a range of useful transformations including carbon-hydrogen bond functionalization and cross-coupling reactions. In addition to this, these studies will aid in the characterization of reactive species during catalytic transformations using the tools of in situ crystallography and spectroscopy. Drs. Bloch and Powers will continue to work to increase diversity in science by bringing excitement of synthetic chemistry research to a broad audience through local and regional educational experiences, including the development of an annual online school on X-ray powder diffraction for undergraduate and graduate students. This collaborative project is targeting the development of new porous materials for site-isolated and solid-state organometallic chemistry. While designer porous solids such as zeolites and metal-organic frameworks have shown incredible promise as heterogeneous catalysts, general platforms for the development of solid-state organometallic chemistry within confined spaces remain elusive. This work seeks to combine charged, permanently porous coordination cages with complementary-charged reactive organometallic fragments for the preparation of a new class of reactive catalysts, porous salts. During this funding period, Bloch and Powers will elucidate the general structure-function properties of porous salts where cage charge, geometry, and functional group presentation will be leveraged to tune salt structure and porosity. Subsequently, Bloch and Powers will use these salts as platforms to incorporate designer reactive ions into porous solids where small molecule binding and activation will be studied to assess salt activity. Reactions to be studied will include C-H bond functionalization and cross-coupling catalysis. Finally, the Bloch/Powers team will utilize straightforward layer-by-layer growth to prepare optically transparent, chemically addressable films which will be used for solid-state photochemical transformations. 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.