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

Abstract

Applying metal–organic frameworks (MOFs) on the surface of other materials to form multifunctional materials has recently attracted great attention; however, directing the MOF overgrowth is challenging due to the orders of magnitude differences in structural dimensions. In this work, we developed a universal strategy to mediate MOF growth on the surface of metal nanoparticles (NPs), by taking advantage of the dynamic nature of weakly adsorbed capping agents. During this colloidal process, the capping agents gradually dissociate from the metal surface, replaced in situ by the MOF. The MOF grows to generate a well-defined NP-MOF interface without a trapped capping agent, resulting in a uniform core–shell structure of one NP encapsulated in one single-crystalline MOF nanocrystal with specific facet alignment. The concept was demonstrated by coating ZIF-8 and UiO-66-type MOFs on shaped metal NPs capped by cetyltrimethylammonium surfactants, and the formation of the well-defined NP-MOF interface was monitored by spectroscopies. The defined interface outperforms ill-defined ones generated via conventional methods, displaying a high selectivity to unsaturated alcohols for the hydrogenation of an α,β-unsaturated aldehyde. This strategy opens a new route to create aligned interfaces between materials with vastly different structural dimensions.

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

“…2(c)). In order to obtain the porous coordination polymer (PCP) crystals with higher-order structure, the shaped nanoparticle cores should play two roles, i.e., metal source and architecture-directing agent for the subsequent spatial organization or morphological replacement of PCP architecture with nanoparticle encapsulation and hierarchical porosity [35]. Moreover, a well-defined nanoparticle-MOF interface was prepared by replacing the dynamic dissociated and weakly adsorbed capping agents such as cetyltrimethylammonium surfactants.…”

“…The key challenges for the construction of nanostructure@MOFs composites are summarized below [1,2,35]. Firstly, the complete encapsulation of nanoparticles within the MOF framework.…”

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

“…The key to the generation of these direct interfaces can be found in the weakly adsorbed capping agent, CTAB, employed by Prof. Tsung. , Capping agents such as long-chain hydrocarbon surfactants (e.g., oleylamine) adsorb on the NP surface via strongly electron-donating moieties, such as −NH 2 , −CO, or −SH, making them hard to remove from the NP surface and preventing direct contact between NP and MOF. Though they could be removed through harsh treatments, such as ozone exposure or high-temperature thermal annealing, these approaches can damage NP structure and lead to NP aggregation.…”

“…In another work, Prof. Tsung also demonstrated the potential impact of a welldefined interface for Au NPs encapsulated in another MOF, UiO-66, which showed >99.0% selectivity for the semihydrogenation of cinnamaldehyde to the desired cinnamyl alcohol, outperforming an ill-defined structure synthesized through more conventional methods. 82 This understanding further highlights the impact that controlled, clean organic− inorganic hybrid interfaces can have on the catalytic performance of NP-MOF composites.…”

The structure and electronic effects of ZIF-8 and ZIF-67 supported Pt catalysts for crotonaldehyde selective hydrogenation

“…Recently, the interfacial interaction between MNPs and metal nodes or aromatic linkers in MOFs has received increasing attention, which would affect the activity and selectivity of catalysts significantly, especially in a,b-unsaturated aldehyde selective hydrogenation. 21 For example, Li et al 22 reported that Pt nanoparticles were surrounded by aryl groups in MIL-100 and transferred electrons to Pt through p bond or ligand interactions, thus improving the selectivity of CQO bond hydrogenation. The electron transfer from the active metals to metal nodes in MOFs reduced the electron density of Pt, which was favourable for the adsorption of the CQO bond.…”