Probing the Interface between Encapsulated Nanoparticles and Metal–Organic Frameworks for Catalytic Selectivity Control

Abstract

Encapsulating metal nanoparticles (NPs) in metal− organic frameworks (MOFs) to control catalytic selectivity has recently attracted great attention; however, an understanding of the NP−MOF interface is lacking. In this work, we used spectroscopy to investigate the interfacial structure and then demonstrate its impact on selectivity. Metal NPs were encapsulated in MOFs using three approaches, impregnation, coating, and one-pot methods. Chemical interactions at the interface were probed through IR and Raman spectroscopy. The fine differences between the interfacial structures generated by the three methods affected their selectivity for the hydrogenation of crotonaldehyde. The direct interface generated by the one-pot method provides the highest selectivity toward the desired crotyl alcohol. This work provides a spectroscopic protocol to study hybrid interfaces and sheds light on their design for effective NP−MOF catalysts.

Creating an Aligned Interface between Nanoparticles and MOFs by Concurrent Replacement of Capping Agents

“…Applying the MOF coating on metals to promote selectivity of the hydrogenation of CO bonds has been observed in many studies, ,− and several mechanisms have been proposed such as steric effect . While these mechanisms are different, a direct NP-MOF interface is required for the MOF layer to modulate the intermediates because the reaction takes place on the surface of metals . With this information in mind, we carried out the hydrogenation of cinnamaldehyde over four catalysts, Au NPs with no MOF coating (Au-on-SiO 2 ), Au NPs on the external surface of MOF (Au-on-MOF), Au NPs with an indirect MOF interface, and Au NPs with a direct MOF interface (see SI for details).…”

“…53 While these mechanisms are different, a direct NP-MOF interface is required for the MOF layer to modulate the intermediates because the reaction takes place on the surface of metals. 54 With this information in mind, we carried out the hydrogenation of cinnamaldehyde over four catalysts, Au NPs with no MOF coating (Au-on-SiO 2 ), Au NPs on the external surface of MOF (Au-on-MOF), Au NPs with an indirect MOF interface, and Au NPs with a direct MOF interface (see SI for details). To compare their selectivity, the loading of each catalyst was controlled to give the same conversion (Table S3).…”

Nanostructure@metal-organic frameworks (MOFs) for catalytic carbon dioxide (CO2) conversion in photocatalysis, electrocatalysis, and thermal catalysis

“…The defined interface of one nanostructure@one MOF nanocrystal provides a high selectivity to unsaturated alcohols in aldehyde catalytic hydrogenation reaction, compared with the conventional preparation method. The strategy is universal to construct aligned and well-defined interfaces between materials with diverse structural dimensions [36]. iv) The MOFs and nanoparticles can be individually prepared, and the nanostructure@MOFs can be achieved by subsequent mixing of the two components (Fig.…”

Tailoring Heterogeneous Catalysts at the Atomic Level: In Memoriam, Prof. Chia-Kuang (Frank) Tsung

“…(g) Selectivity for crotonaldehyde hydrogenation of Pt NPs obtained through each method. Adapted with permission from ref . Copyright 2021 American Chemical Society.…”

“…To fill this knowledge gap, Prof. Tsung established spectroscopic protocols to investigate the interfacial structure by combining IR and Raman spectroscopy, using these techniques to demonstrate the impact of interfacial structure on crotonaldehyde hydrogenation (Figure 6). 81 Only the samples with welldefined NP-MOF interfaces showed selectivity (70.4%) toward the desired unsaturated product, crotyl alcohol, whereas those formed through conventional coating methods, with an illdefined interface, showed poor (9.8%) crotyl alcohol selectivity. Raman analysis demonstrated the presence of interfacial polyvinylpyrrolidone (PVP), suggesting that the illdefined NP-MOF interface can be attributed to capping agents trapped between the NP and MOF.…”