Metal Organic Frameworks as Heterogeneous Catalysts in Olefin Epoxidation and Carbon Dioxide Cycloaddition

Pd NPs decorated on crosslinked sodium alginate modified iron-based metal-organic framework Fe(BTC) as a green multifunctional catalyst for the oxidative amidation

The primary objective of this investigation was to develop a new nanocatalyst that could produce amides by oxidative amidation of benzyl alcohol, thereby reducing its environmental harm. To achieve this, Pd nanoparticle-immobilized crosslinked sodium alginate-modified iron-based metal-organic framework Fe(BTC) (Fe(BTC)@SA/ED/Pd), with excellent activity and selectivity in modified oxidative amidation of benzyl alcohol with amines, has been described. Crosslinked sodium alginate was modified on iron-based metal-organic framework Fe(BTC). It is worth noting that Pd nanoparticles were immobilized for the first time on a novel nanocomposite based on the Fe(BTC) MOF and crosslinked sodium alginate for tandem oxidative amidation to improve the eco-friendliness and economic efficiency of the process. The synergic effects of Fe(BTC), sodium alginate, and Pd NPs are important factors influencing the catalytic activity. Easy and green synthesis methods, availability of materials, high Pd loading, available catalytic sites, high surface area, high selectivity, and simple separation from the reaction medium are effective properties in catalytic activity.

Postsynthetic Modification of Amine-Functionalized MIL-101(Cr) Metal-Organic Frameworks with an EDTA-Zn(II) Complex as an Effective Heterogeneous Catalyst for Hantzsch Synthesis of Polyhydroquinolines

The present work aims at preparing the EDTA-Zn(II) complex-supported on the amine-functionalized MIL-101(Cr) MOF-as a new and effective heterogenized catalyst. The optimization of the hydrothermal process shows that 120 °C is the best condition to grow the MIL-101(Cr)-NH2 MOF crystals. Moreover, regarding the use of the postsynthetic modification (PSM) method, hexadentate EDTA was grafted on this support via a simple aminolysis process before further coordinating it with Zn ions to create the corresponding Zn(II) catalytic complex. The catalytic activity of this compound was then investigated in the context of a one-pot synthesis of polyhydroquinolines. This approach has a number of advantages including the following: the use of a solvent that is not hazardous, applying a porous catalyst that is inexpensive, secure, and recyclable; rapid reaction times, high levels of efficiency, and the simplicity of MOF catalyst separation. Accordingly, the process in question can be given the label of "green chemistry".

Dual-Ligand Strategy for the Design and Construction of a Cd-Zn Heterometallic Metal-Organic Framework by One-Pot Synthesis as a Heterogeneous Catalyst for the Epoxidation Reaction of Olefins

The use of metal-organic frameworks (MOFs) as catalysts is reported in various industrial applications. In contrast to monometallic MOFs, heterometallic MOFs with mixed organic ligands showed enhanced catalytic properties. The catalytic properties of heterometallic MOFs can be enhanced by generating defects and the synergistic effect between the two heterometals at secondary building units. By using a solvothermal technique, a Cd-Zn heterometallic MOF with a new morphology, [Cd2Zn(DPTTZ)0.5(OBA)3(H2O)(HCOOH)] (IUST-4) [DPTTZ = 2,5-di(4-pyridyl)thiazolo[5,4-d]thiazole, OBA = 4,4'-oxybis(benzoic acid)], was synthesized via a mixed-ligand strategy and characterized by single-crystal and powder X-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, and thermogravimetric analysis. X-ray crystallographic analysis showed that IUST-4 is a neutral 3D metal-organic framework crystallized in the monoclinic system with space group C2/c. In this study, the catalytic properties of IUST-4 for the epoxidation of cyclooctene were investigated. IUST-4 was selected as the optimal catalyst for epoxy product production due to its high selectivity and yield. Moreover, the catalytic performance of IUST-4 was maintained despite five recycling cycles without significant degradation. The epoxidation of cyclooctene with IUST-4 has several advantages, including good selectivity, easy recovery, and short-time reaction.

An Fe3O4 supported O-phenylenediamine based tetraaza Schiff base-Cu(ii) complex as a novel nanomagnetic catalytic system for synthesis of pyrano[2,3-c]pyrazoles

In this research, we present a post-synthetic method for synthesizing a novel nanomagnetic Cu(II) Schiff base complex and investigate its efficiency in catalytic organic conversion reactions. Various spectroscopic analyses were employed to characterize the physiochemical characteristics of the resulting nanocomposite. The experimental results successfully demonstrate the catalytic application of the prepared Cu-complex in the preparation of pyrano[2,3-c]pyrazole heterocycles. This synthesis involved a one-pot three-component condensation reaction, wherein hydrazine hydrate, ethyl acetoacetate, malononitrile, and aromatic aldehydes were combined under reflux conditions using water as the solvent. Notably, the heterogenized complex exhibited exceptional catalytic performance, achieving remarkable conversion rates and selectivity, all accomplished using only 12 mg of the catalyst. Furthermore, thorough stability assessments of this catalyst were conducted through reusability and hot filtration tests, which confirmed its non-leaching properties and demonstrated excellent results over the course of five consecutive runs.

Coordination Polymers from an Amino-Functionalized Terphenyl-Tetracarboxylate Linker: Structural Multiplicity and Catalytic Properties

An amino-functionalized terphenyl-tetracarboxylic acid, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4tpta), was used as an adaptable linker to synthesize, under hydrothermal conditions, eight coordination polymers (CPs). The obtained products were formulated as [Co(μ6-H2tpta)]n (1), [Co(μ3-H2tpta)(2,2'-bipy)]n (2), [M3(μ6-Htpta)2(2,2'-bipy)2]n (M = Mn (3), Cd (4)), [Ni2(μ4-tpta)(phen)2(H2O)4]n (5), [Zn2(μ6-tpta)(phen)2]n (6), {[Zn2(μ6-tpta)(μ-4,4'-bipy)]·H2O}n (7), and [Zn2(μ6-tpta)(μ-H2biim)(H2O)2]n (8), wherein 2,2'-bipyridine (2,2'-bipy), 4,4'-bipyridine (4,4'-bipy), 1,10-phenanthroline (phen), or 2,2'-biimidazole (H2biim) are present as additional stabilizing ligands. The structural types of 1-8 vary from one-dimensional (1D) (2, 5) and two-dimensional (2D) (3, 4, 6) CPs to three-dimensional (3D) metal-organic frameworks (MOFs) (1, 7, and 8) with a diversity of topologies. The products 1-8 were investigated as catalysts in the Knoevenagel condensation involving aldehydes and active methylene derivatives (malononitrile, ethyl cyanoacetate, or tert-butyl cyanoacetate), leading to high condensation product yields (up to 99%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were investigated. This work broadens the application of H4tpta as a versatile tetracarboxylate linker for the generation of diverse CPs/MOFs.

Phenylalanine-Based Co2+ and Cd2+ 1D Coordination Polymers: Structural Properties and Catalytic Application for Solvent-Free Aerobic Oxidation of Cycloalkene

Two 1D coordination polymers (CPs) with general formula [M(L)(H2O)(AcO)]n, (M = Co (1) or Cd (2), AcO = acetate anion and L denotes l-phenylalanine based ligand), were synthesized and fully characterized by various spectroscopies (UV-vis, FTIR, and NMR), thermal techniques, magnetic measurements (for 1), and single-crystal and powder X-ray diffraction studies. They can be described as "ribbon-like" 1D polymers constructed through a zigzag arrangement. The polymeric structure is developed due to the coordination mode adopted by the amino acid ligand, classified as μ3-N1O1:O1:O2, which simultaneously links three metal centers. This moiety also plays an important role as a magnetic coupler between metal centers in the cobalt system, which shows a weak antiferromagnetic interaction. Both CPs have also been used in the catalytic oxidation of cyclohexene with molecular oxygen (O2) as an oxidant. Under mild conditions, both compounds demonstrated remarkable catalytic activity, with the cobalt system being more efficient than the cadmium analogue (conversion: 73 and 58% and selectivity for the major product, 2-cyclohexanone: 63 and 55%, for 1 and 2, respectively). Leaching experiments and the results obtained using a radical quencher are consistent with a radical-mediated mechanism for the Co compound. The presence of the superoxide radical was also confirmed using EPR spectroscopy and DMPO as a spin trap, which was further validated by DFT calculations. The activity observed for the Cd analogue is attributed to the organic scaffold assisted by the templating effect of the metal ion.

CuI nanoparticle-immobilized on a hybrid material composed of IRMOF-3 and a sulfonamide-based porous organic polymer as an efficient nanocatalyst for one-pot synthesis of 2,4-diaryl-quinolines

As a significant class of synthetic and natural products with multiple biological activities, quinolines are used in medical and electronic devices. In this study, a novel method is presented to synthesize 2,4-diarylquinoline derivatives via a simple one-pot multicomponent reaction between phenylacetylenes, aniline derivatives, and aldehydes in CH₃CN using IRMOF-3/PSTA/Cu. Notably, polymer/MOF is stabilized through a reaction between a sulfonamide-triazine-based porous organic polymer [poly (sulfonamide-triazine)](PSTA) and an amino-functionalized zinc metal-organic framework (IRMOF-3). Next, the prepared nanocomposites (IRMOF-3/PSTA) are modified using copper iodide nanoparticles (CuI NPs). Overall, the high product yields, facile recovery of nanocatalysts, short reaction times, and broad substrate range make this process environmentally friendly, practical, and economically justified.

Synthesis of UiO-66-Sal-Cu(OH)2 by a Simple and Novel Method: MOF-Based Metal Thin Film as a Heterogeneous Catalyst for Olefin Oxidation

Metal-organic frameworks (MOFs), particularly UiO-66-NH₂, are employed as a catalyst in many industrial catalyst applications. As converting catalysts into thin film significantly increases their catalytic properties for the epoxidation of olefins, we report a general approach to synthesizing MOF thin films (UiO-66-Sal-Cu(OH)₂). Using the postsynthesis method (PSM), UiO-66-NH₂ was functionalized with salicylaldehyde and entrapped on copper hydroxide nanoparticle surfaces using a modern strategy (MOF thin film). We used field-emission scanning electron microscopy (FE-SEM), EDX (energy-dispersive X-ray analysis), XRD (X-ray diffraction), FT-IR (Fourier transform infrared), BET (Brunauer-Emmett-Teller), TGA (thermogravimetric analysis), XPS (X-ray photoelectron spectroscopy), and ICP-MS (inductively coupled plasma mass spectrometry) to determine the structure and morphology of the synthesized UiO-66-Sal-Cu(OH)₂. The oxidation of cyclooctene by the UiO-66-Sal-Cu(OH)₂ thin film was studied. Due to its advantages, such as being environmentally friendly (base metal-loaded catalyst, room temperature, solvent-free reaction), reusability, and high yield, this compound can be an appropriate catalyst for the oxidation of olefins.

Cu(ii) immobilized on poly(guanidine-sulfonamide)-functionalized Bentonite@MgFe2O4: a novel magnetic nanocatalyst for the synthesis of 1,4-dihydropyrano[2,3-c]pyrazole†

In this paper, we aim at synthesizing a new nanocomposite material in which bentonite acts as a nucleation site for MgFe₂O₄ nanoparticles precipitation in the attendance of an external magnetic field (MgFe₂O₄@Bentonite). Moreover, poly(guanidine-sulfonamide), as a novel kind of polysulfonamide, was immobilized on the surface of the prepared support (MgFe₂O₄@Bentonite@PGSA). Finally, an efficient and environment-friendly catalyst (containing nontoxic polysulfonamide, copper, and MgFe₂O₄@Bentonite) was prepared by anchoring a copper ion on the surface of MgFe₂O₄@Bentonite@PGSAMNPs. The synergic effect of MgFe₂O₄ magnetic nanoparticles (MNPs), bentonite, PGSA, and copper species was observed while conducting the control reactions. The synthesized Bentonite@MgFe₂O₄@PGSA/Cu, which was characterized using energy-dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier-transform infrared (FT-IR) spectroscopy, was applied as a highly efficient heterogeneous catalyst to synthesize 1,4-dihydropyrano[2,3-c] pyrazole yielding up to 98% at 10 minutes. Excessive yield, quick reaction time, using water solvent, turning waste to wealth, and recyclability are the important advantages of the present work.

In this paper, we aim at synthesizing a new nanocomposite material in which bentonite acts as a nucleation site for MgFe₂O₄ nanoparticles precipitation in the attendance of an external magnetic field (MgFe₂O₄@Bentonite).

Polymeric Copper(II) Complexes with a Newly Synthesized Biphenyldicarboxylic Acid Schiff Base Ligand—Synthesis, Structural and Thermal Characterization

The newly synthesized biphenyldicarboxylic acid Schiff base and its complexes with Cu(II) were synthesized, and their spectroscopic and structural analysis was performed. The reaction of the ligand and copper(II) acetate in different solvents resulted in the formation of two solvatomorphic complexes, one with MeOH, and the other with DMF molecules, in the crystal lattice. The differences in the results of the thermal analysis could be explained by the different polarities of the solvents present. SC-XRD analysis revealed that the ligand is coordinated as a dianion, in a pentadentate manner, through two phenoxide oxygen atoms, two azomethine nitrogen atoms, and with the oxygen atom of one carboxylate functioning as a bridge that connects the monomeric units. The coordination polyhedron was described with several parameters obtained from different methods of calculation. The presence of different solvents in the crystal structure results in differences in the H-bond networks, and an overall different crystal packing of the structural units in the obtained complexes.

Cornerstones in Contemporary Inorganic Chemistry

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Metal-Organic Frameworks Decorated Cu2O Heterogeneous Catalysts for Selective Oxidation of Styrene

The selective oxidation of styrene with highly efficient, environmentally benign, and cost-effective catalysts are of great importance for sustainable chemical processes. Here, we develop an in situ self-assembly strategy to decorate Cu-based metal-organic framework (MOF) Cu-BDC-NH2 nanocrystals on Cu2O octahedra to construct a series of Cu2O@Cu-BDC-NH2 catalysts for selective oxidation of styrene. Using H2O2 as green oxidants, the optimized sample of Cu2O@Cu-BDC-NH2-8h could achieve 85% styrene conversion with 76% selectivity of benzaldehyde under a mild condition of 40 °C. The high performance of the as-prepared heterogeneous catalysts was attributed to the well-designed Cu+/Cu2+ interface between Cu2O and Cu-BDC-NH2 as well as the porous MOF shells composed of the uniformly dispersed Cu-BDC-NH2 nanocrystals. The alkaline properties of Cu2O and the –NH2 modification of MOFs enable the reaction to be carried out in a base-free condition, which simplifies the separation process and makes the catalytic system more environmentally friendly. Besides the Cu2O octahedra (od-Cu2O), the Cu2O cuboctahedrons (cod-Cu2O) were synthesized by adjusting the added polyvinyl pyrrolidone, and the obtained cod-Cu2O@Cu-BDC-NH2 composite also showed good catalytic performance. This work provides a useful strategy for developing highly efficient and environmentally benign heterogeneous catalysts for the selective oxidation of styrene.