時間：2025-11-03(一) 10:10 am

講題：Arrays of Clusters of Atomically Precise Composition for Heterogeneous Catalysis

講者：Prof. Joseph T. Hupp

服務單位：Northwestern University, U.S.A.

地點：4樓創意講堂

主持人：龔仲偉 副教授

摘要 :

         For many gas-phase chemical and condensed-phase electrochemical transformations, rate acceleration by heterogeneous catalysts is indispensable. Such catalysts often rely upon precious-metal components – making them expensive.  Further, they often comprise non-uniform collections of active sites, i.e. sites presenting differing facets, differing geometries, and/or differing numbers of functional atoms, situated on non-uniform supports and residing in non-uniform chemical and physical environments. These non-uniformities can greatly complicate both characterization of catalyst structures and elucidation of catalysis mechanisms. The resulting uncertainties weaken links between theory and experiment, obscure structure/activity correlations, and impede exploitation of computational methods to design or discover superior catalysts. Desirable would be much more chemically and structurally ideal collections of heterogeneous catalysts composed of earth-abundant elements.

        This presentation will focus on the synthesis of uniformly supported and distributed arrays of catalytic clusters having atomically precise compositions. Array organization is based upon installation/grafting of clusters into size-matched pores of crystalline metal-organic framework (MOF) materials. Notably, the employed, high-surface-area MOFs are reasonably thermally stable (e.g., up to ~720 K) and chemically robust (e.g., retention of crystallinity & porosity following prolonged exposure to steam, corrosive vapors (NH₃, H₂S, PH₃), or O₂, and following prolonged immersion in aqueous acid, aq. hydrogen peroxide, selected ionic liquids, or nonaqueous organic solvents,  including strongly coordinating solvents and electrolyte-loaded solvents). The catalysts of most interest to us are: a) known, or easily envisioned, polyoxometalates (POMs), presented in gas-phase environments, and b) previously unknown polythiometalates (PTMs) that, nevertheless, are functionally reminiscent of active-sites of enzymes having high competency for reduction reactions.  Representative catalytic reactions are vapor-phase conversion of CO₂ to methanol; semi-hydrogenation of alkynes via H₂-derived, sulfur-vacancy-stabilized, metal hydrides; low-temperature oxidation of hydrocarbons by vacancy-activated O₂; and reduction of ¹⁵N₂ to ¹⁵NH₃ at ambient temperature and pressure, via the intermediacy of water-derived, molybdenum-stabilized hydrides.

        EDX measurements show that catalytic clusters are distributed throughout the high-surface-area interiors of the employed MOFs. By yielding fairly precise pictures of cluster siting within frameworks, X-ray-diffraction-based DED (difference electron density) measurements inform about catalyst accessibility and about active-site steric & chemical environments. X-ray-photoelectron-spectroscopy (XPS) and synchrotron-enabled X-ray absorption (XANES and EXAFS) measurements provide information about catalyst evolution. Extraordinarily detailed catalyst structural information, i.e. comparable to that from single-crystal X-ray diffraction measurements, is obtainable from disordered arrays by combining the results of computational modeling of candidate structures (by the Getman group at Ohio State Univ.) and pair-distribution function analysis of total-X-ray-scattering (by the Chapman group at Stony Brook Univ.).

         Finally, measurements of reaction rates, reaction orders, and product distributions, together with operando spectroscopic measurements and DFT-based modeling, provide information about mechanisms of catalysis, and, in turn, insight into the design of superior, framework-organized & stabilized, catalysts.

學歷 :

Michigan State University, U.S.A. 化學博士 (1983)
Houghton College, U.S.A. 化學學士 (1979)

經歷：

Morrison Professor of Chemistry, Northwestern University (2000-present)
Professor, Department of Chemistry, Northwestern University (1993-present)
Associate Professor, Department of Chemistry, Northwestern University (1990-1993)
Assistant Professor, Department of Chemistry, Northwestern University (1986-1990)

榮譽：

1. 美國文理科學院(American Academy of Arts and Sciences)院士 (2021)
2. Allen J. Bard Award, The Electrochemical Society (2023)
3. Chair of Editorial Board, Energy & Environmental Science (2019-2022)
4. Associate Editor, Journal of the American Chemical Society (2003-2014)
5. Clarivate Analytics/Thomson-Reuter高引用學者 (2014-2024)