Session: Chemistry of Materials:

Exploring novel materials as heterogeneous catalysts could improve the technological landscape through allowing access to pharmaceutical chemicals and improving current industrial processes. In this regard, metal-organic frameworks (MOFs) have gained wide-spread interest as heterogeneous catalysts, as they can provide a unique avenue to precisely control active site geometry and ensemble sizes on the nanoscale. MOFs are crystalline extended solids that can possess high porosity and surface area (e.g., >1000 m² g⁻¹), thereby providing sufficient, dispersed metal nodes available for catalytic reactions. In this poster, hydrogenation catalysis studies of a heterometallic MOF, (Cu_xRh_1−x)₃(BTC)₂ (BTC³⁻ = 1,3,5-benzenetricarboxylate), will be presented.
Initial results demonstrate that the MOF scaffold can stabilize an unusual +2 oxidation state for Rh ions, that was confirmed through both X-ray photoelectron spectroscopy and X-ray absorption near edge structure. Up to this point, Rh²⁺ had not been previously reported in crystalline MOFs. Through employment of a flow-bed reactor system, (Cu_xRh_1−x)₃(BTC)₂ catalyzed a propylene hydrogenation reaction with relatively high activity (>1500 µmol g catalyst⁻¹ min⁻¹) and selectivity, compared to other heterometallic MOFs that did not exhibit significant hydrogenation activity. (Cu_xRh_1−x)₃(BTC)₂ also exhibited excellent stability under catalytic and reducing conditions, and density functional theory (DFT) calculations were employed to gain insight into the mechanism of hydrogenation at Rh²⁺ MOF nodes.

Overall, the results presented provide a fundamental understanding of design principles towards MOF catalysts, proof of concept in a flow-bed reactor system, and could help guide the rational construction of future heterogeneous catalysts.

Donna Chen

Appearances