(327e) Electronic Effects on Open Framework Material-Encapsulated Metal Nanoparticles (NP@OFM) and Implications on Catalysis

Authors: 
Gomez Gualdron, D., Colorado School of Mines
Schweitzer, B., Colorado School of Mines
Archuleta, C., Colorado School of Mines
A current grand challenge of catalysis involves performing reactions with high selectivity to increase yield and efficiency of artificial catalysts in cost-effective manner. In this regard, a promising approach to impart exceptional chemoselectivity to catalytic nanoparticles (NPs) is to enshroud them with a surrounding porous shell made of open framework materials such as metal-organic frameworks (MOFs) [1]. This shell, mimicking catalytic processes in enzymes, can sterically force orientations of reactants in a particular way to make certain catalytic pathways more favorable. However, optimizing the OFM-NP combination for a desired reaction is a daunting task for experimentalists, due the millions of potential combinations to choose from and the amount of work needed to synthesize any particular combination to test it in the lab. Thus, molecular simulations are key for accelerated evaluation of possible OFM-NP combinations that can inform targets for catalyst synthesis and testing.

Toward this goal it is necessary to understand what the most crucial effects that need to be considered at the design (or computational screening) stage are. Previous studies have decoupled steric effects in NP@MOFs systems from other factors [2-4] and provided insights on how these effects can affect reactivity. However, partly due to insufficient understanding of the structure of the NP/OFM interface, the role of electronic effects originating from the interaction of OFM components and the metal at the NP/OFM interface have yet to be studied. Leveraging recent insights on the interface structure [5], here we discuss ongoing work in our lab to elucidate the relative importance of electronic effects originating from the mentioned interactions compared to electronic effects originating from changes in NP composition. We study this with the assistance of periodic DFT calculations to elucidate how charge is transferred between the OFM and the NP depending on the kind of bonds occurring at the interface, the chemical functionality of the OFM, and the composition of the metal. Thus, the effect of interactions at the interface and NP composition on the catalyst electronic density of state (DOS) and on the binding of small, common catalytic species (e.g. C*, H3C*, O*, HO*, N*, H*) to the NP surface has been evaluated, also considering implications on catalytic rates (e.g. via available scaling relationships).

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