MOF Catalyst Research Articles

One-pot synthesis of bimetal MOFs as highly efficient catalysts for selective oxidation of styrene

A series of novel bimetallic organic framework materials (Cux-Coy-MOF) have been successfully prepared by a simple one-pot synthetic method, and their characters were evaluated via means of various techniques. The tested data showed a series of Cux-Coy-MOFs displayed good crystallinity and the doping of Co in original Cu-based framework would not change the morphology of the MOF catalysts. The catalytic activity of prepared materials was tested in the catalytic oxidation of styrene in the presence of TBHP. The effects of reaction time, reaction temperature and other reaction conditions on catalytic performance were systematically studied. The results revealed that the introduction of Co can improve the selectivity to form epoxides and reduce the yield of benzaldehyde without affecting the conversion rate of catalytic oxidation reaction of styrene. Excitingly, the Cu0.25-Co0.75-MOF showed better catalytic performance than Cu-MOF and Co-MOF under the optimal reaction conditions, the conversion rate of styrene reached 97.81%, and styrene oxide selectivity reached 83.04%, which indicated a significant synergistic effect of the Cu/Co bimetallic MOF. Furthermore, the Cu0.25-Co0.75-MOF catalyst exhibited good reusability that could be reused at least four times without significant inactivation. A series of novel bimetallic organic framework materials (Cux-Coy-MOF) have been successfully prepared via a simple one-pot synthetic method, and they exhibited high activity and selectivity as catalyst towards for oxidation of styrene.

Fabrication of copper centered metal organic framework and nitrogen, sulfur dual doped graphene oxide composite as a novel electrocatalyst for oxygen reduction reaction

The main focus of this study is to synthesize a free – platinum electrocatalyst for ORR applications. Since the price of copper is much lower than platinum, the Copper - centered Metal Organic Framework (Cu - MOF) is selected as the electrocatalyst. The electron conductivity of MOFs is low. Accordingly, in order to enhance the ORR kinetics and electrochemistry activity, for the first time, Nitrogen and Sulfur Dual-Doped Reduced Graphene Oxide (NS - RGO) with different concentrations are incorporated into the Cu – MOF structure. In other words, NS-RGO has high electrical conductivity which can operate as an efficient carrier for electron transfer. For evaluating the structural properties and morphology of synthesized electrocatalysts, six main characterization techniques, consist of XRD, FESEM, Raman, EDS, TEM, and FTIR are employed. Also, in order to assess the durability and ORR activity, the electrochemical measurements are performed. The electrochemical tests are implemented using the Rotary Disk Electrode (RDE) device in the alkaline medium. Based on the achieved results, the best ORR activity is related to the 8% NS – RGO - Cu – MOF catalyst. The onset potential and electron transferred number (n) of this catalyst are obtained to be −0.06 V vs Ag/AgCl and 3.53, respectively. In other words, it tends to favor the 4e-pathway for ORR. In this project, the relationship between structure and electrochemistry activity of non-precious metal/carbon composites is investigated. materials Finally, the electrochemistry activity of synthesized electrocatalysts is compared to the previous investigations and commercial 20 wt% Pt/C. These comparisons indicated that mixing different concentrations of NS-RGO with Cu-MOF can improve the electrochemistry activity of MOFs considerably. Actually, the NS – RGO - Cu – MOF composite can be considered as a new cost-effective electrocatalyst that can help to the development of fuel cell technology.

Synthesis Cu(I)–CN-based MOF with in-situ generated cyanogroup by cleavage of acetonitrile: Highly efficient for catalytic cyclization of propargylic alcohols with CO2

Developing a highly effective process for synthesis a cyano-bridged compound to avoid toxic organic or inorganic cyanides is very significant method for alleviating cyanides pollution. Here, a CN-based MOF catalyst (Cu(I)–CN–BPY) was synthesized by using copper ions coupled with Na4W10O32 in CH3CN under solvothermal conditions. The cyano-groups are generated in situ from the cleavage of C(sp3)–C(sp) in CH3CN. Because Cu(I) sites have ability to activate π-activate internal alkynes of carbon–carbon triple bonds for carboxylic cyclization reactions, which was applied in the cyclization of propargylic alcohols with CO2 and exhibited high efficiency with >95 % yields. For seeking out the active sites of MOF structure in carboxylic cyclization, we also synthesized two MOFs of Cu(I)–Cl–BPY and Cu(I)–I–BPY, and investigated for this reaction.

Highly stable and efficient visible-light-driven carbon dioxide reduction by zirconium–metalloporphyrin PCN-222 via dual catalytic routes

The zirconium–metalloporphyrin PCN-222-Zn has been synthesized and studied as catalysts for photoreduction of CO2. Compared to the pure PCN-222, the PCN-222-Zn exhibited largely enhanced formate formation rate. Remarkably, the addition of Zn(II) ions (0.5 wt%) to the PCN-222 significantly increased the formate yield rate from 28.65 μmol/g/h to 354.14 μmol/g/h after 4 h reaction, which was highest reported value among Zr-based MOFs. The fluorescence spectroscopy indicated the better charge carrier separation efficiency for PCN-222-Zn. Also, the superior CO2 uptake abilities of PCN-222-Zn further explained the enhanced activity. We assumed that the Zr-oxo cluster and the metalloporphyrin linker formed dual photocatalytic routes. Besides, the uncoordinated porphyrin rings in 5% PCN-222-Zn can facilitate re-bonding of the broken Zn–N bonds during the photoreduction reaction, which guaranteed the long-lasting activity. This study may provide a new strategy to design novel MOF catalysts for CO2 reduction.

Stacked nano rods of cobalt and nickel based metal organic frame work of 2–amino benzene dicarboxylic acid for photocatalytic hydrogen generation

Stacked nanorods of cobalt and nickel based hetero bimetallic organic frameworks (MOFs) of 2–amino benzene dicarboxylic acid are developed as photocatalyst for hydrogen evolution reaction. The ratio of metals in the catalyst is tuned to achieve a narrow band gap, and the MOF with optimized Ni to Co ratio of 1: 0.5 (1Ni0.5Co@NH2BDC) exhibited the lowest band gap (2.2 eV) and electron–hole recombination rate. The catalyst exhibits enhanced photocatalytic activity for hydrogen evolution reaction due to the absorption of photons by 2–amino benzene dicarboxylic acid and excitation of electrons from HOMO to LUMO of the organic linker. The excited electrons relay to the cluster of the framework and reduce the protons gather around the cluster to hydrogen. The holes in the HOMO state are occupied by the electrons from the sacrificial agents and it supports the photocatalytic hydrogen evolution by avoiding electron–hole recombination. The stability of MOF catalyst in water splitting medium even with sacrificial agents confirms its competency with the state–of–the–art photocatalytic materials.

Highly Active Heterogeneous PdCl2/MOF Catalyst for Suzuki–Miyaura Cross‐Coupling Reactions of Aryl Chloride

The exploration of highly efficient Pd/MOF heterogeneous catalyst system for the Suzuki–Miyaura cross‐coupling (SMC) reactions of aryl chlorides is still challenging. Herein, a PdCl2/UiO‐67‐bpydc was successfully synthesized by immobilizing a low amount of PdCl2 onto the zirconium‐based MOF (UiO‐67‐bpydc). PdCl2/UiO‐67‐bpydc showed excellent catalytic performance and good recycle ability for the SMC reaction of aryl chlorides under an ambient condition. Furthermore, PdCl2/UiO‐67‐bpydc retains the high catalytic activity even after five cycles, and exhibited excellent substrate size selectivity.

Efficient Removal of Thallium from Flue Gas Using Manganese-Based MOF Catalysts by Gas–Solid Phase Catalytic Oxidation and Adsorption

Thallium (Tl) is known to be extremely toxic. However, thallium pollution from smelting tail gas has long been neglected as an environmental issue. This study aims to develop a gaseous thallium con...

Chiral Proline-Decorated Bifunctional Pd@NH2-UiO-66 Catalysts for Efficient Sequential Suzuki Coupling/Asymmetric Aldol Reactions

The design and development of site-isolating and multifunctional catalysts for multistep sequential reactions at the molecular level is a significant challenge. Herein, we first report bifunctional metal NPs@chiral MOFs catalysts for asymmetric sequential reactions. Pd nanoparticles and chiral proline were successfully added to NH2-UiO-66 to construct two chiral bifunctional catalysts, in which active Pd nanoparticles were encapsulated into the frameworks via the "bottle-around-ship" method, and chiral proline was introduced into NH2-UiO-66 by coordination to zirconium nodes and postsynthetic modification (PSM) of the organic linkers. The chiral proline-decorated bifunctional Pd@NH2-UiO-66 catalysts were applied to sequential Suzuki coupling/asymmetric aldol reactions with excellent coupling performance (yields up to 99.9%) and good enantioselectivities (eeanti values up to 97%). The heterogeneous catalyst by coordination of proline can be reused, and the reaction activity was not significantly reduced after four cycles.

Kinetic modeling of oleic acid esterification with UiO-66: from intrinsic experimental data to kinetics via elementary reaction steps

This work reports the experimental conversion of oleic acid (OA) into methyl oleate via UiO-66 MOF catalyst. Strong focus is on the kinetic modeling: 67 models, based on elementary reaction steps for Eley-Rideal, Langmuir-Hinshelwood and Hattori kinetic mechanisms, are proposed. Via the application of initial reaction rate theory and nonisothermal kinetic modeling, one model adequately describes the experimental data. It is a variant on the Eley-Rideal type of model, such that the surface reaction includes the oleic acid adsorbate, methanol reacts from the liquid phase and one additional active site is considered to make the ester and water as surface reaction products, so that overall two active sites are used in the surface reaction. An activation energy of 54.9 ± 1.8 kJ mol−1 is reported and the desorption of the ester was found to be irreversible. In addition, NH3 TPD revealed at least two types of acid sites (#) on the UiO-66 MOF, from which turnover rates were calculated in the range of 2.54 ± 0.33 to 8.82 ± 0.87 mmolOA mol#−1 s−1. Since the catalyst is recyclable and no additional acids have to be used, this system can be considered as a green alternative for the well-known homogeneously catalyzed esterification reaction.

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble-Metal-Free [Zn116 ] Nanocages.

The reaction of propargylic amines and CO2 can provide high-value-added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco-friendly noble-metal-free MOFs catalysts. Here, a giant and lantern-like [Zn116 ] nanocage in zinc-tetrazole 3D framework [Zn22 (Trz)8 (OH)12 (H2 O)9 ⋅8 H2 O]n Trz=(C4 N12 O)4- (1) was obtained and structurally characterized. It consists of six [Zn14 O21 ] clusters and eight [Zn4 O4 ] clusters. To our knowledge, this is the highest-nuclearity nanocages constructed by Zn-clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2 , exclusively affording various 2-oxazolidinones under mild conditions. It is the first eco-friendly noble-metal-free MOFs catalyst for the cyclization of propargylic amines with CO2 . DFT calculations uncover that ZnII ions can efficiently activate both C≡C bonds of propargylic amines and CO2 by coordination interaction. NMR and FTIR spectroscopy further prove that Zn-clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.

Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble‐Metal‐Free [Zn116] Nanocages

AbstractThe reaction of propargylic amines and CO2 can provide high‐value‐added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco‐friendly noble‐metal‐free MOFs catalysts. Here, a giant and lantern‐like [Zn116] nanocage in zinc‐tetrazole 3D framework [Zn22(Trz)8(OH)12(H2O)9⋅8 H2O]n Trz=(C4N12O)4− (1) was obtained and structurally characterized. It consists of six [Zn14O21] clusters and eight [Zn4O4] clusters. To our knowledge, this is the highest‐nuclearity nanocages constructed by Zn‐clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2, exclusively affording various 2‐oxazolidinones under mild conditions. It is the first eco‐friendly noble‐metal‐free MOFs catalyst for the cyclization of propargylic amines with CO2. DFT calculations uncover that ZnII ions can efficiently activate both C≡C bonds of propargylic amines and CO2 by coordination interaction. NMR and FTIR spectroscopy further prove that Zn‐clusters play an important role in activating C≡C bonds of propargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.

Cycloaddition of Propargylic Amines and CO2 by Ni@Pd Nanoclusters Confined Within Metal–Organic Framework Cavities in Aqueous Solution

The bio-metal–organic framework (bio-MOF) notion along with nanoparticles catalysts of Ni@Pd core–shell magnetic for carbon dioxide conversion is made by l-glutamic acid that is the natural substitute for combinatorial ligands, and illustrated their catalytic effect, in the propargylic amines cyclization with carbon dioxide for obtaining 2-oxazolidinones, completed to the correlation of structure–DFT. This nano Ni@Pd that consists of catalyst is detected using ICP, XRD, TGA, TEM, FT-IR, and VSM. The zinc-glutamate-MOF or ZnGlu is properly proved as the MOF catalyst in the case of the propargylic amines cyclization with carbon dioxide for obtaining 2-oxazolidinones, in addition, its performance is compared to those of outstanding synthetic MOFs stated in the method. The produced catalyst done even at moist state, is thermally as well as chemically firm; easily separable, heterogeneous, because of high selectivity of it, lack of mixture solvents, and also simple catalyst recovery using outside magnet. It is recycled until ten times. Ni@Pd/ZnGlu MNPs dramatically improves the availability of the nanoparticle levels in comparison whit the common substrate because of its 3D hierarchical construction. Ni@Pd/ZnGlu MNPs, because of their economic environmental and economic parameters, are considered as the future of MOF chemistry in industry. Cycloaddition of propargylic amines and CO2 by Ni@Pd nanoclusters confined within metal−organic framework cavities in aqueous solution.

Metal–organic frameworks of Cu2(TPTC)-catalyzed cascade C–S coupling/Csp2–H hydroxylation reaction

This paper reports a novel disulfide-directed Csp2–H hydroxylation cascade reaction strategy catalyzed by Cu2(TPTC), a metal–organic framework material with binuclear Cu(II) paddlewheel nodes. In the strategy, Cu2(TPTC) MOF can effectively catalyze the coupling reaction of disulfide and arylboronic acid, and realize the disulfide-directed Csp2–H hydroxylation reaction. This reaction proceeded well under Cu2(TPTC) MOF catalyst with good yields, which provides an efficient method to the synthesis of functional organic molecules, such as 2-(phenylthio)phenols derivatives.

Cellulose stabilized Fe3O4and carboxylate‐imidazole and Co‐based MOF growth as an exceptional catalyst for the Knoevenagel reaction

In this study, Fe3O4nanoparticles were functionalized with cellulose, and then hybridized with cobalt (II)‐based metal‐organic framework (Co‐MOF) containing carboxylate and imidazole functionalities. FTIR, XRD, FE‐SEM, TEM, BET, EDX, VSM and STA analyses were used to characterize the synthesized samples. The resultant Fe3O4/cellulose/Co‐MOF nanocomposite was applied efficiently as a powerful and economic heterogeneous catalyst in the condensation of a variety of different aromatic aldehydes with malononitrile under solvent‐free conditions at room temperature for 10 min and offered the corresponding coupling products in high yields. The catalyst could be straightforwardly separated by a magnet from the reaction mixture and reused without a noteworthy drop in catalytic activity at least five times. The use of Fe3O4/cellulose/Co‐MOF catalyst outcomes under mild reaction conditions in very short reaction time, outstanding catalytic activity, high recyclability and an easy work‐up process for Knoevenagel condensation.

Post‐synthetic Modification of DUT‐5‐based Metal Organic Frameworks for the Generation of Single‐site Catalysts and their Application in Selective Epoxidation Reactions

AbstractNew single‐site catalysts based on mixed‐linker metal‐organic frameworks with DUT‐5 structure, which contain immobilized Co2+, Mn2+ and Mn3+ complexes, have successfully been synthesized via post‐synthetic modification. 2,2’‐Bipyridine‐5,5’‐dicarboxylate linkers were directly metalated, while 2‐amino‐4,4’‐biphenyldicarboxylate linkers were post‐synthetically modified by their conversion to Schiff‐base ligands and a subsequent immobilization of the metal complexes. The resulting materials were used as catalysts in the selective epoxidation of trans‐stilbene and the activities and selectivities of the different catalysts were compared. The influence of various reaction parameters on conversion, yield and selectivity were investigated. Very low catalyst amounts of 0.02 mol % were sufficient to obtain a high conversion of trans‐stilbene using molecular oxygen from air as the oxidant. For cobalt‐containing MOF catalysts, conversions up to 90 % were observed and, thus, they were more active than their manganese‐containing counterparts. Recycling experiments and hot filtration tests proved that the reactions were mainly catalyzed via heterogeneous pathways.

Cyclic metal(oid) clusters control platinum-catalysed hydrosilylation reactions: from soluble to zeolite and MOF catalysts.

The Pt-catalysed addition of silanes to functional groups such as alkenes, alkynes, carbonyls and alcohols, i.e. the hydrosilylation reaction, is a fundamental transformation in industrial and academic chemistry, often claimed as the most important application of Pt catalysts in solution. However, the exact nature of the Pt active species and its mechanism of action is not well understood yet, particularly regarding regioselectivity. Here, experimental and computational studies together with an ad hoc graphical method show that the hydroaddition of alkynes proceeds through Pt–Si–H clusters of 3–5 atoms (metal(oid) association) in parts per million amounts (ppm), which decrease the energy of the transition state and direct the regioselectivity of the reaction. Based on these findings, new extremely-active (ppm) microporous solid catalysts for the hydrosilylation of alkynes, alkenes and alcohols have been developed, paving the way for more environmentally-benign industrial applications.

A new approach to the mechanism for the acetalization of benzaldehyde over MOF catalysts

The benzaldehyde acetalization catalyzed by UiO-66 and UiO-66F, was carried out in a batch-type reactor at room temperature and atmospheric pressure, and the full kinetic study was performed using the Langmuir–Hinshelwood and Eley–Rideal models.

Organic synthesis of high added value molecules with MOF catalysts.

Recent examples of organic synthesis of fine chemicals and pharmaceuticals in confined spaces of MOFs are highlighted and compared with silica-based ordered porous solids, such as zeolites or mesoporous (organo)silica. These heterogeneous catalysts offer the possibility of stabilizing the desired transition states and/or intermediates during organic transformations of functional groups and (C-C/C-N) bond forming steps towards the desired functional high added value molecular scaffolds. A short introduction on zeolites, mesoporous silica and metal-organic frameworks is followed by relevant applications in which confined active sites in the pores promote single or multi-step organic synthesis of industrially relevant molecules. A critical discussion on the catalytic performances of the different types of hybrid inorganic-organic catalysts in the synthesis of O- and N-containing acyclic and heterocyclic molecules has been presented.

Bimetal-organic framework MIL-53(Co-Fe): an efficient and robust electrocatalyst for the oxygen evolution reaction.

Rationally designing high-efficiency catalysts for the oxygen evolution reaction (OER) is extremely important for developing sustainable energy technologies, but remains a major research challenge. In this paper, a Co/Fe-imidazole-based bimetal-organic framework nanosheet array grown on a nickel foam [MIL-53(Co-Fe)/NF] was prepared via a facile solvothermal process. Surprisingly, MIL-53(Co-Fe)/NF shows excellent OER activity with overpotential as low as 262 mV at 100 mA cm-2, much lower than those of the single metal-based MOFs, and even comparable to that of the precious RuO2. The results indicate that the synergetic effect of co-doped Fe and Co makes a crucial contribution to the high activity of the bimetal-based MOF catalyst. Additionally, this catalyst also displays outstanding long-term electrochemical durability for at least 80 h.

Preparation of MOF catalysts and simultaneously modulated metal nodes and ligands via a one-pot method for optimizing cycloaddition reactions

MOFs were adjusted with metal nodes and ligands to endow them with Lewis acids and Brønsted acids for enhanced cycloaddition reactions.