Metal‐Organic Frameworks as Catalyst Supports: Influence of Lattice Disorder on Metal Nanoparticle Formation

Abstract

Because of their high tunability and surface area, metal-organic frameworks (MOFs) show great promise as supports for metal nanoparticles. Depending on the synthesis route, MOFs may contain defects. Here, we show that highly crystalline MIL-100(Fe) and disordered Basolite® F300, with identical iron 1,3,5-benzenetricarboxylate composition, exhibit very divergent properties when used as a support for Pd nanoparticle deposition. While MIL-100(Fe) shows a regular MTN-zeotype crystal structure with two types of cages, Basolite® F300 lacks long-range order beyond 8 Å and has a single-pore system. The medium-range configurational linker-node disorder in Basolite® F300 results in a reduced number of Lewis acid sites, yielding more hydrophobic surface properties compared to hydrophilic MIL-100(Fe). The hydrophilic/hydrophobic nature of MIL-100(Fe) and Basolite® F300 impacts the amount of Pd and particle size distribution of Pd nanoparticles deposited during colloidal synthesis and dry impregnation methods, respectively. It is suggested that polar (apolar) solvents/precursors attractively interact with hydrophilic (hydrophobic) MOF surfaces, allowing tools at hand to increase the level of control over, for example, the nanoparticle size distribution.

Stepwise collapse of a giant pore metal–organic framework

“…7 inset]. This is consistent with those previously reported by Weckhuysen et al 46 Furthermore, the use of synchrotron radiation in this study provided us with extremely high real-space resolution, and so additional peaks at 2.98, 4.38 and 5.32 Å were also able to be resolved. The first and second of these were assigned to Fe-C distances.…”

“…[43][44][45] Non-local density functional theory (NL-DFT) can be used to extract pore size distributions from nitrogen adsorption isotherms. 46,47 Classical fluid density functional theory is used to construct adsorption isotherms in ideal pore geometries and then solve the adsorption integral equation. 48 Several inherent limitations persist however, including the absence of a specific kernel available for MOFs.…”

Tuning the Properties of MOF‐808 via Defect Engineering and Metal Nanoparticle Encapsulation

“…More recently, the tuning of the hydrophilicity of MOF crystals via defect engineering for efficient oil/water separation has been demonstrated in Zr‐based UiO‐66 [23] . The enhancement in catalytic activity has also been achieved by preparing a so‐called “composite MOF” or “metal@MOF” by metal impregnation [24] or metal encapsulation [25, 26] . Similarly, tuning of the catalytic properties of MFI‐type zeolites has been suggested following the incorporation of Mo at defect sites within the structure [27] .…”

Mixed‐Metal MOF‐74 Templated Catalysts for Efficient Carbon Dioxide Capture and Methanation

“…Nanoparticles have been introduced into MOFs via several methods including solution infiltration, chemical vapor deposition, and solid grinding. [ 4 ] Undesirably, these approaches often lead to large nanoparticles forming on the exterior of the MOF framework due to incomplete infiltration of the metal precursors, inhibiting their usefulness as a catalyst. [ 5 ] Atomic layer deposition has been used to control the formation of nanoparticles within MOF pores.…”

“…In situations where metal nanoparticles have been successfully included in MOF pores, the resulting composite materials have been successfully applied to hydrogenation reactions, highlighting the implicit benefit of preserving the MOF architecture for catalysis. [ 4b,7 ] However, the formation of these composite structures often requires cumbersome preparation techniques, limiting their translation into industrially relevant catalytic processes.…”