Controlling Catalytic Properties of Pd Nanoclusters through Their Chemical Environment at the Atomic Level Using Isoreticular Metal–Organic Frameworks

Abstract

Control of heterogeneous catalytic sites through their surrounding chemical environment at an atomic level is crucial to catalyst design. We synthesize Pd nanoclusters (NCs) in an atomically tunable chemical environment using isoreticular metal-organic framework (MOF) supports (Pd@UiO-66-X, X = H, NH 2 , OMe). In an aerobic reaction between benzaldehyde and ethylene glycol, these catalysts show product distributions that are completely altered from the acetal to the ester when we change the functional groups on the MOF linkers from −NH 2 to −H/-OMe. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies, along with density functional theory (DFT) calculations, show that the coordination of the −NH 2 groups to the Pd NCs could weaken their oxidation capability to a greater extent in comparison to that of the −OMe group. Moreover, the limited number of −NH 2 groups per cavity in the MOF change the electronic properties of the Pd NCs while still leaving open sites for catalysis.

Engineering UiO‐66 Metal Organic Framework for Heterogeneous Catalysis

“…[90] For instance, Pd NPs were encapsulated in isoreticular MOFs of UiO-66-X (Pd@UiO-66-X, X=H, NH 2 , OMe) and it was observed that Pd@UiO-66-NH 2 favors the formation of acetal, while Pd@UiO-66 and Pd@UiO-66-OMe lead to a higher selectivity to the ester ( Figure 13). [90] For instance, Pd NPs were encapsulated in isoreticular MOFs of UiO-66-X (Pd@UiO-66-X, X=H, NH 2 , OMe) and it was observed that Pd@UiO-66-NH 2 favors the formation of acetal, while Pd@UiO-66 and Pd@UiO-66-OMe lead to a higher selectivity to the ester ( Figure 13).…”

Implications of sterically constrained n-butane oxidation reactions on the reaction mechanism and selectivity to 1-butanol

“…3) could provide. UiO-66 is a good candidate MOF to encapsulate catalysts [25] due to its stability (decomposition temperature N773 K) [32]. UiO-66 has fcu pore topology with "large" octahedral cages (ca.…”

“…This process is exothermic for θ O b 0. 25 [46,48]. The dissociation is exothermic (−0.39 eV) with a relatively low barrier (0.66 eV) on the triangle configuration (θ O = 0.25 ML) due to the availability of a "free" fcc site, i.e., a vacancy in the p(2 × 2)-O lattice due to one O atom in that lattice being out of place.…”

“…A number of examples of NP@MOF catalysts have been reported in the literature, but the development of such catalysts has thus far relied on experimental work [13,[18][19][20][21][22][23][24][25][26]. This is partly due to the computationally prohibitive size of fully atomistic models of the NP/MOF interface for density functional theory (DFT) calculations, and partly due to the unknown structural details of the interface.…”

Fischer–Tropsch synthesis over MOF-supported cobalt catalysts (Co@MIL-53(Al))

“…[36][37][38][39] Furthermore, some NPs@MOFs nanohybrids demonstrate excellent catalytic activities in organic reactions due to the confinement effect of the MOF crystalline pore structure which prevents metal nanoparticles from sintering. [40][41][42][43][44] However, the examples of the successful incorporation of Co NPs in MOF porous host matriсes are rather scarce, 45 probably, because the reduction of a cobalt precursor to metallic NPs demands more severe conditions than those used for noble metals. Actually, a weak point of a majority of MOF materials is a low thermal stability (as a rule, below ~ 350°C), which limits their application as carriers for heterogeneous catalysts.…”