Tracking Rh Atoms in Zeolite HY: First Steps of Metal Cluster Formation and Influence of Metal Nuclearity on Catalysis of Ethylene Hydrogenation and Ethylene Dimerization

DFT Study of the Mechanism of Selective Hydrogenation of Acetylene by Rhodium Single-Atom Catalyst Supported on HY Zeolite

The selectivity of acetylene hydrogenation by the Rh single-atom catalyst (SAC) supported on HY zeolite was investigated using density functional theory (DFT) and a 5/83T quantum mechanics/molecular mechanics (QM/MM) embedded cluster model. The calculated activation barrier (ΔG≠) for the oxidative addition of dihydrogen to the Rh metal center (15.9 kcal/mol) is lower in energy than that for the σ-bond metathesis of dihydrogen to the Rh-C bond (22.7 kcal/mol) and the Rh-O bond (28.4 kcal/mol). The activation barriers of the oxidative addition of subsequent dihydrogen molecules are significantly higher than that of the oxidative addition of the first dihydrogen molecule. These findings align with the experimentally observed activity and selectivity of the atomically dispersed Rh catalyst supported on HY zeolite. Natural bond orbital (NBO), molecular orbital (MO) and fuzzy bond order analyses were used to examine the interaction between the Rh metal center and acetylene versus ethylene ligands. The occupancies of the Rh lone pairs, π-bonding and π*-antibonding orbitals of acetylene and ethylene are consistent with the expected stronger interaction between the Rh metal center and acetylene compared to ethylene on the HY zeolite support.

Challenges and Opportunities for Exploiting the Role of Zeolite Confinements for the Selective Hydrogenation of Acetylene

Zeolites, with their ordered crystalline porous structure, provide a unique opportunity to confine metal catalysts, whether single atoms (e.g., transition metal ions (TMIs)) or metal clusters, when used as a catalyst support. The confined environment has been shown to provide rate and selectivity enhancement across a variety of reactions via both steric and electronic effects, such as size exclusion and transition state stabilization. In this review, we provide a survey of various zeolite confined catalysts used for the semihydrogenation of acetylene highlighting their performance, defined by ethylene selectivity at full acetylene conversion, in relationship to the synthesis technique employed. Synthesis methods that ensure confinement with the catalyst transition metal location in the extra-framework positions are reported to have the highest selectivity to ethylene. However, the underlying molecular factors responsible for selective catalysis within confinement remain elusive due to the difficulty in deconvoluting individual effects. Through the careful use of a combination of characterization and spectroscopic methods, insights into the relationship between the properties of zeolite confined catalysts and their performance have been explored in other works for a variety of reactions. More specifically, operando spectroscopy studies have revealed the dynamic behavior of zeolite confined catalysts under various conditions implying that the structure and properties observed ex situ do not always match those of the active catalyst under reaction conditions. Applying this type of analysis to acetylene semihydrogenation, a simple gas phase reaction, can help elucidate the structure-function relationship of zeolite confined catalysts allowing for more informed design choices and consequently their application to a wider variety of more complex reactions such as the liquid phase hydrogenation of alkynols where solvent effects must also be considered in addition to those of confinement.

Probing Basal and Prismatic Planes of Graphitic Materials for Metal Single Atom and Subnanometer Cluster Stabilization

Supported metal single atom catalysis is a dynamic research area in catalysis science combining the advantages of homogeneous and heterogeneous catalysis. Understanding the interactions between metal single atoms and the support constitutes a challenge facing the development of such catalysts, since these interactions are essential in optimizing the catalytic performance. For conventional carbon supports, two types of surfaces can contribute to single atom stabilization: the basal planes and the prismatic surface; both of which can be decorated by defects and surface oxygen groups. To date, most studies on carbon-supported single atom catalysts focused on nitrogen-doped carbons, which, unlike classic carbon materials, have a fairly well-defined chemical environment. Herein we report the synthesis, characterization and modeling of rhodium single atom catalysts supported on carbon materials presenting distinct concentrations of surface oxygen groups and basal/prismatic surface area. The influence of these parameters on the speciation of the Rh species, their coordination and ultimately on their catalytic performance in hydrogenation and hydroformylation reactions is analyzed. The results obtained show that catalysis itself is an interesting tool for the fine characterization of these materials, for which the detection of small quantities of metal clusters remains a challenge, even when combining several cutting-edge analytical methods.

Bimetallic Metal Sites in Metal-Organic Frameworks Facilitate the Production of 1-Butene from Electrosynthesized Ethylene

Converting CO2 to synthetic hydrocarbon fuels is of increasing interest. In light of progress in electrified CO2 to ethylene, we explored routes to dimerize to 1-butene, an olefin that can serve as a building block to ethylene longer-chain alkanes. With goal of selective and active dimerization, we investigate a series of metal-organic frameworks having bimetallic catalytic sites. We find that the tunable pore structure enables optimization of selectivity and that periodic pore channels enhance activity. In a tandem system for the conversion of CO2 to 1-C4H8, wherein the outlet cathodic gas from a CO2-to-C2H4 electrolyzer is fed directly (via a dehumidification stage) into the C2H4 dimerizer, we study the highest-performing MOF found herein: M' = Ru and M″ = Ni in the bimetallic two-dimensional M'2(OAc)4M″(CN)4 MOF. We report a 1-C4H8 production rate of 1.3 mol gcat-1 h-1 and a C2H4 conversion of 97%. From these experimental data, we project an estimated cradle-to-gate carbon intensity of -2.1 kg-CO2e/kg-1-C4H8 when CO2 is supplied from direct air capture and when the required energy is supplied by electricity having the carbon intensity of wind.

Dynamic structural evolution of MgO-supported palladium catalysts: from metal to metal oxide nanoparticles to surface then subsurface atomically dispersed cations

Supported noble metal catalysts, ubiquitous in chemical technology, often undergo dynamic transformations between reduced and oxidized states-which influence the metal nuclearities, oxidation states, and catalytic properties. In this investigation, we report the results of in situ X-ray absorption spectroscopy, scanning transmission electron microscopy, and other physical characterization techniques, bolstered by density functional theory, to elucidate the structural transformations of a set of MgO-supported palladium catalysts under oxidative treatment conditions. As the calcination temperature increased, the as-synthesized supported metallic palladium nanoparticles underwent oxidation to form palladium oxides (at approximately 400 °C), which, at approximately 500 °C, were oxidatively fragmented to form mixtures of atomically dispersed palladium cations. The data indicate two distinct types of atomically dispersed species: palladium cations located at MgO steps and those embedded in the first subsurface layer of MgO. The former exhibit significantly higher (>500 times) catalytic activity for ethylene hydrogenation than the latter. The results pave the way for designing highly active and stable supported palladium hydrogenation catalysts with optimized metal utilization.

Suppressing Metal Leaching and Sintering in Hydroformylation Reaction by Modulating the Coordination of Rh Single Atoms with Reactants

Hydroformylation reaction is one of the largest homogeneously catalyzed industrial processes yet suffers from difficulty and high cost in catalyst separation and recovery. Heterogeneous single-atom catalysts (SACs), on the other hand, have emerged as a promising alternative due to their high initial activity and reasonable regioselectivity. Nevertheless, the stability of SACs against metal aggregation and leaching during the reaction has rarely been addressed. Herein, we elucidate the mechanism of Rh aggregation and leaching by investigating the structural evolution of Rh1@silicalite-1 SAC in response to different adsorbates (CO, H2, alkene, and aldehydes) by using diffuse reflectance infrared Fourier transform spectroscopy, X-ray adsorption fine structure, and scanning transmission electron microscopy techniques and kinetic studies. It is discovered that the aggregation and leaching of Rh are induced by the strong adsorption of CO and aldehydes on Rh, as well as the reduction of Rh3+ by CO/H2 which weakens the binding of Rh with support. In contrast, alkene effectively counteracts this effect by the competitive adsorption on Rh atoms with CO/aldehyde, and the disintegration of Rh clusters. Based on these results, we propose a strategy to conduct the reaction under conditions of high alkene concentration, which proves to be able to stabilize Rh single atom against aggregation and/or leaching for more than 100 h time-on-stream.

Review and perspectives on TS-1 catalyzed propylene epoxidation

Titanium silicate zeolite (TS-1) is widely used in the research on selective oxidations of organic substrates by H2O2. Compared with the chlorohydrin process and the hydroperoxidation process, the TS-1 catalyzed hydroperoxide epoxidation of propylene oxide (HPPO) has advantages in terms of by-products and environmental friendliness. This article reviews the latest progress in propylene epoxidation catalyzed by TS-1, including the HPPO process and gas phase epoxidation. The preparation and modification of TS-1 for green and sustainable production are summarized, including the use of low-cost feedstocks, the development of synthetic routes, strategies to enhance mass transfer in TS-1 crystal and the enhancement of catalytic performance after modification. In particular, this article summarizes the catalytic mechanisms and advanced characterization techniques for propylene epoxidation in recent years. Finally, the present situation, development prospect and challenge of propylene epoxidation catalyzed by TS-1 were prospected.

Ethene Hydroformylation Catalyzed by Rhodium Dispersed with Zinc or Cobalt in Silanol Nests of Dealuminated Zeolite Beta

Catalysts for hydroformylation of ethene were prepared by grafting Rh into nests of ≡SiOZn-OH or ≡SiOCo-OH species prepared in dealuminated BEA zeolite. X-ray absorption spectra and infrared spectra of adsorbed CO were used to characterize the dispersion of Rh. The Rh dispersion was found to increase markedly with increasing M/Rh (M = Zn or Co) ratio; further increases in Rh dispersion occurred upon use for ethene hydroformylation catalysis. The turnover frequency for ethene hydroformylation measured for a fixed set of reaction conditions increased with the fraction of atomically dispersed Rh. The ethene hydroformylation activity is 15.5-fold higher for M = Co than for M = Zn, whereas the propanal selectivity is slightly greater for the latter catalyst. The activity of the Co-containing catalyst exceeds that of all previously reported Rh-containing bimetallic catalysts. The rates of ethene hydroformylation and ethene hydrogenation exhibit positive reaction orders in ethene and hydrogen but negative orders in carbon monoxide. In situ IR spectroscopy and the kinetics of the catalytic reactions suggest that ethene hydroformylation is mainly catalyzed by atomically dispersed Rh that is influenced by Rh-M interactions, whereas ethene hydrogenation is mainly catalyzed by Rh nanoclusters. In situ IR spectroscopy also indicates that the ethene hydroformylation is rate limited by formation of propionyl groups and by their hydrogenation, a conclusion supported by the measured H/D kinetic isotope effect. This study presents a novel method for creating highly active Rh-containing bimetallic sites for ethene hydroformylation and provides new insights into the mechanism and kinetics of this process.

Emerging Applications of Synchrotron Radiation X-Ray Techniques in Single Atomic Catalysts

Single atom catalysts (SACs) can achieve a maximum atom utilization efficiency of 100%, which provides significantly increased active sites compared with traditional catalysts during catalytic reactions. Synchrotron radiation technology is an important characterization method for identifying single-atom catalysts. Several types of internal information, such as the coordination number, bond length and electronic structure of metals, can all be analyzed. This review will focus on the introduction of synchrotron radiation techniques and their applications in SACs. First, the fundamentals of synchrotron radiation and the corresponding techniques applied in characterization of SACs will be briefly introduced, such as X-ray absorption near edge spectroscopy and extended X-ray absorption fine structure spectroscopy and in situ techniques. The detailed information obtained from synchrotron radiation X-ray characterization is described through four routes: 1) the local environment of a specific atom; 2) the oxidation state of SACs; 3) electronic structures at different orbitals; and 4) the in situ structure modification during catalytic reaction. In addition, a systematic summary of synchrotron radiation X-ray characterization on different types of SACs (noble metals and transition metals) will be discussed.

Observation and Characterization of Dicarbonyls on a RhCu Single-Atom Alloy

Dicarbonyl species are ubiquitous on Rh/oxide catalysts and are known to form on Rh⁺ centers. However, dicarbonyl species have never been directly observed on single-atom alloys (SAAs) where the active site is metallic. Herein, using surface science and theoretical modeling, we provide evidence of dicarbonyl species at isolated Rh sites on a RhCu(100) SAA. This approach not only enables us to directly visualize dicarbonyl species at Rh sites but also demonstrates that the transition between the mono- and dicarbonyl configuration can be achieved by changing surface temperature and CO pressure. Density functional theory calculations further support the mono- and dicarbonyl assignments and provide evidence that these species should be stable on other SAA combinations. Together, these results provide a picture of the structure and energetics of both the mono- and dicarbonyl configurations on the RhCu(100) SAA surface and should aid with IR assignments on SAA nanoparticle catalysts.

In situ synthesis of Pt nanoparticles encapsulated in Silicalite-1 zeolite via a steam-assisted dry-gel conversion method

In this work, Pt nanoparticles (NPs) were directly encapsulated into MFI-type zeolite (Pt@S-1) via a steam-assisted dry-gel conversion method. The synthesis process included the disaggregation of Pt immobilized SiO2-SH spheres...

Thermodynamically driven self-formation of Ag nanoparticles in Zn-embedded carbon nanofibers for efficient electrochemical CO2 reduction

The electrochemical CO₂ reduction reaction (CO₂RR), which converts CO₂ into value-added feedstocks and renewable fuels, has been increasingly studied as a next-generation energy and environmental solution. Here, we report that single-atom metal sites distributed around active materials can enhance the CO₂RR performance by controlling the Lewis acidity-based local CO₂ concentration. By utilizing the oxidation Gibbs free energy difference between silver (Ag), zinc (Zn), and carbon (C), we can produce Ag nanoparticle-embedded carbon nanofibers (CNFs) where Zn is atomically dispersed by a one-pot, self-forming thermal calcination process. The CO₂RR performance of AgZn–CNF was investigated by a flow cell with a gas diffusion electrode (GDE). Compared to Ag–CNFs without Zn species (53% at −0.85 V vs. RHE), the faradaic efficiency (FE) of carbon monoxide (CO) was approximately 20% higher in AgZn–CNF (75% at −0.82 V vs. RHE) with 1 M KOH electrolyte.

Ag nanoparticles in Zn-embedded carbon nanofiber were synthesized by a simple one-pot, self-forming strategy. Charged Zn single atoms act as Lewis acidic sites and improving the CO₂ reduction reaction performance of the Ag nanoparticles.

Transformation of atomically dispersed platinum in SAPO-37 into platinum clusters: catalyst for ethylene hydrogenation

Atomically dispersed supported platinum catalysts were synthesized by the reaction of Pt(acac)2 (acac = acetylacetonato) with the silicoaluminophosphate molecular sieve SAPO-37, with infrared spectra showing that the reaction involved SAPO OH groups.

Metal@Zeolite Hybrid Materials for Catalysis

The fixation of metal nanoparticles into zeolite crystals has emerged as a new series of heterogeneous catalysts, giving performances that steadily outperform the generally supported catalysts in many important reactions. In this outlook, we define different noble metal-in-zeolite structures (metal@zeolite) according to the size of the nanoparticles and their relative location to the micropores. The metal species within the micropores and those larger than the micropores are denoted as encapsulated and fixed structures, respectively. The development in the strategies for the construction of metal@zeolite hybrid materials is briefly summarized in this work, where the rational preparation and improved thermal stability of the metal nanostructures are particularly mentioned. More importantly, these metal@zeolite hybrid materials as catalysts exhibit excellent shape selectivity. Finally, we review the current challenges and future perspectives for these metal@zeolite catalysts.

Ligand Stabilized Ni1 Catalyst for Efficient CO Oxidation

Supported single transition metal (TM₁ ) catalysts have attracted broad attention in academia recently. Still, their corresponding reactivity and stability under reaction conditions are critical but have not well explored at the fundamental level. Herein, we use density functional theory calculation and ab initio molecular dynamics simulation to investigate the role of reactants and ligands on the reactivity and stability of graphitic carbon nitride (g-C₃ N₄ ) supported Ni₁ for CO oxidation. We find out that supported bare Ni₁ atoms are only metastable on the surface and tend to diffuse into the interlayer of g-C₃ N₄ . Though Ni₁ is catalytically active at moderate temperatures, CO adsorption induced dimerization deactivates the catalyst. Hydroxyl groups not only are able to stabilize the supported Ni₁ atom, but also increase the reactivity by participating directly in the reaction. Our results provide valuable insights on improving the chemical stability of TM₁ by ligands without sacrificing the reactivity, which are helpful for the rational design of highly loaded atomically dispersed supported metal catalysts.

New Strategies for the Preparation of Sinter-Resistant Metal-Nanoparticle-Based Catalysts

Supported metal nanoparticles are widely used as catalysts in the industrial production of chemicals, but still suffer from deactivation because of metal leaching and sintering at high temperature. In recent years, serious efforts have been devoted to developing new strategies for stabilizing metal nanoparticles. Recent developments for preparing sinter-resistant metal-nanoparticle catalysts via strong metal-support interactions, encapsulation with oxide or carbon layers and within mesoporous materials, and fixation in zeolite crystals, are briefly summarized. Furthermore, the current challenges and future perspectives for the preparation of highly efficient and extraordinarily stable metal-nanoparticle-based catalysts, and suggestions regarding the mechanisms involved in sinter resistance, are proposed.

The Comparison between Single Atom Catalysis and Surface Organometallic Catalysis

Single atom catalysis (SAC) is a recent discipline of heterogeneous catalysis for which a single atom on a surface is able to carry out various catalytic reactions. A kind of revolution in heterogeneous catalysis by metals for which it was assumed that specific sites or defects of a nanoparticle were necessary to activate substrates in catalytic reactions. In another extreme of the spectrum, surface organometallic chemistry (SOMC), and, by extension, surface organometallic catalysis (SOMCat), have demonstrated that single atoms on a surface, but this time with specific ligands, could lead to a more predictive approach in heterogeneous catalysis. The predictive character of SOMCat was just the result of intuitive mechanisms derived from the elementary steps of molecular chemistry. This review article will compare the aspects of single atom catalysis and surface organometallic catalysis by considering several specific catalytic reactions, some of which exist for both fields, whereas others might see mutual overlap in the future. After a definition of both domains, a detailed approach of the methods, mostly modeling and spectroscopy, will be followed by a detailed analysis of catalytic reactions: hydrogenation, dehydrogenation, hydrogenolysis, oxidative dehydrogenation, alkane and cycloalkane metathesis, methane activation, metathetic oxidation, CO₂ activation to cyclic carbonates, imine metathesis, and selective catalytic reduction (SCR) reactions. A prospective resulting from present knowledge is showing the emergence of a new discipline from the overlap between the two areas.

Noble Metal Particles Confined in Zeolites: Synthesis, Characterization, and Applications

Noble metal nanoparticles or subnanometric particles confined in zeolites, that is, metal@zeolite, represent an important type of functional materials with typical core-shell structure. This type of material is known for decades and recently became a research hotspot due to their emerging applications in various fields. Remarkable achievements are made dealing with the synthesis, characterization, and applications of noble metal particles confined in zeolites. Here, the most representative research progress in metal@zeolites is briefly reviewed, aiming to boost further research on this topic. For the synthesis of metal@zeolites, various strategies, such as direct synthesis from inorganic or ligand-assisted noble metal precursors, multistep postsynthesis encapsulation and ion-exchange followed by reduction, are introduced and compared. For the characterization of metal@zeolites, several most useful techniques, such as electron microscopy, X-ray based spectroscopy, infrared and fluorescence emission spectroscopy, are recommended to check the successful confinement of noble metal particles in zeolite matrix and their unique physiochemical properties. For the applications of metal@zeolites, catalysis and optics are involved with an emphasis on catalytic applications including the size-dependent catalytic properties, the sintering-resistance properties, the substrate shape-selective catalysis, and catalysis modulation by zeolite microenvironment.

End-On Bound Iridium Dinuclear Heterogeneous Catalysts on WO3 for Solar Water Oxidation

Heterogeneous catalysts with atomically defined active centers hold great promise for high-performance applications. Among them, catalysts featuring active moieties with more than one metal atom are important for chemical reactions that require synergistic effects but are rarer than single atom catalysts (SACs). The difficulty in synthesizing such catalysts has been a key challenge. Recent progress in preparing dinuclear heterogeneous catalysts (DHCs) from homogeneous molecular precursors has provided an effective route to address this challenge. Nevertheless, only side-on bound DHCs, where both metal atoms are affixed to the supporting substrate, have been reported. The competing end-on binding mode, where only one metal atom is attached to the substrate and the other metal atom is dangling, has been missing. Here, we report the first observation that end-on binding is indeed possible for Ir DHCs supported on WO₃. Unambiguous evidence supporting the binding mode was obtained by in situ diffuse reflectance infrared Fourier transform spectroscopy and high-angle annular dark-field scanning transmission electron microscopy. Density functional theory calculations provide additional support for the binding mode, as well as insights into how end-on bound DHCs may be beneficial for solar water oxidation reactions. The results have important implications for future studies of highly effective heterogeneous catalysts for complex chemical reactions.

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles

Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal-support interaction, and metal-reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results obtained from different systems and try to give a picture on how different types of metal species work in different reactions and give perspectives on the future directions toward better understanding of the catalytic behavior of different metal entities (single atoms, nanoclusters, and nanoparticles) in a unifying manner.

Engineering of Transition Metal Catalysts Confined in Zeolites

Transition metal-zeolite composites are versatile catalytic materials for a wide range of industrial and lab-scale processes. Significant advances in fabrication and characterization of well-defined metal centers confined in zeolite matrixes have greatly expanded the library of available materials and, accordingly, their catalytic utility. In this review, we summarize recent developments in the field from the perspective of materials chemistry, focusing on synthesis, postsynthesis modification, (operando) spectroscopy characterization, and computational modeling of transition metal-zeolite catalysts.

Single rhodium atoms anchored in micropores for efficient transformation of methane under mild conditions

Catalytic transformation of CH₄ under a mild condition is significant for efficient utilization of shale gas under the circumstance of switching raw materials of chemical industries to shale gas. Here, we report the transformation of CH₄ to acetic acid and methanol through coupling of CH₄, CO and O₂ on single-site Rh₁O₅ anchored in microporous aluminosilicates in solution at ≤150 °C. The activity of these singly dispersed precious metal sites for production of organic oxygenates can reach about 0.10 acetic acid molecules on a Rh₁O₅ site per second at 150 °C with a selectivity of ~70% for production of acetic acid. It is higher than the activity of free Rh cations by >1000 times. Computational studies suggest that the first C-H bond of CH₄ is activated by Rh₁O₅ anchored on the wall of micropores of ZSM-5; the formed CH₃ then couples with CO and OH, to produce acetic acid over a low activation barrier.

Stable iridium dinuclear heterogeneous catalysts supported on metal-oxide substrate for solar water oxidation

Atomically dispersed catalysts refer to substrate-supported heterogeneous catalysts featuring one or a few active metal atoms that are separated from one another. They represent an important class of materials ranging from single-atom catalysts (SACs) and nanoparticles (NPs). While SACs and NPs have been extensively reported, catalysts featuring a few atoms with well-defined structures are poorly studied. The difficulty in synthesizing such structures has been a critical challenge. Here we report a facile photochemical method that produces catalytic centers consisting of two Ir metal cations, bridged by O and stably bound to a support. Direct evidence unambiguously supporting the dinuclear nature of the catalysts anchored on α-Fe₂O₃ is obtained by aberration-corrected scanning transmission electron microscopy (AC-STEM). Experimental and computational results further reveal that the threefold hollow binding sites on the OH-terminated surface of α-Fe₂O₃ anchor the catalysts to provide outstanding stability against detachment or aggregation. The resulting catalysts exhibit high activities toward H₂O photooxidation.

Molecular Rhodium Complexes Supported on the Metal-Oxide-Like Nodes of Metal Organic Frameworks and on Zeolite HY: Catalysts for Ethylene Hydrogenation and Dimerization

Metal-organic frameworks (MOFs) with nodes consisting of zirconium oxide clusters (Zr₆) offer new opportunities as supports for catalysts with well-defined, essentially molecular, structures. We used the precursor Rh(C₂H₄)₂(acac) (acac is acetylacetonate) to anchor Rh(I) complexes to the nodes of the MOF UiO-67 and, for comparison, to the zeolite dealuminated HY (DAY). These were characterized experimentally by measurement of catalytic activities and selectivities for ethylene hydrogenation and dimerization in a once-through flow reactor at 298 K and 1 bar. The catalyst performance data are complemented with structural information determined by infrared and extended X-ray absorption fine structure spectroscopies and by calculations at the level of density functional theory, the latter carried out also to extend the investigation to a related MOF, NU-1000. The agreement between the experimental and calculated structural metrics is good, and the calculations have led to predictions of reaction mechanisms and associated energetics. The data demonstrate a correlation between the catalytic activity and selectivity and the electron-donor tendency of the supported rhodium (as measured by the frequencies of CO ligands bonded as probes to the Rh(I) centers), which is itself a measure of the electron-donor tendency of the support.