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.

Recent progress in lanthanide metal–organic frameworks and their derivatives in catalytic applications

Research progress in lanthanide metal–organic frameworks and their derivatives in the field of catalysis has been presented on the basis of different organic reactions.

Lanthanide metal–organic frameworks for catalytic oxidation of olefins

Two isostructural metal–organic frameworks (MOFs), termed Ln-MOF-589 (Ln = La, Ce), were developed for the catalytic oxidation of olefins.

CuII- and CoII-Based MOFs: {[La2Cu3(µ-H2O)(ODA)6(H2O)3]∙3H2O}n and {[La2Co3(ODA)6(H2O)6]∙12H2O}n. The Relevance of Physicochemical Properties on the Catalytic Aerobic Oxidation of Cyclohexene

The aerobic oxidation of cyclohexene was done using the heterometallic metal organic frameworks (MOFs) {[La2Cu3(μ-H2O)(ODA)6(H2O)3]⋅3H2O}n (LaCuODA)) (1) and {[La2Co3(ODA)6(H2O)6]∙12H2O}n (LaCoODA) (2) as catalysts, in solvent free conditions (ODA, oxydiacetic acid). After 24 h of reaction, the catalytic system showed that LaCoODA had a better catalytic performance than that of LaCuODA (conversion 85% and 67%). The structures of both catalysts were very similar, showing channels running along the c axis. The physicochemical properties of both MOFs were determined to understand the catalytic performance. The Langmuir surface area of LaCoODA was shown to be greater than that of LaCuODA, while the acid strength and acid sites were greater for LaCuODA. On the other hand, the redox potential of the active sites was related to CoII/CoIII in LaCoODA and CuII/CuI in LaCuODA. Therefore, it is concluded that the Langmuir surface area and the redox potentials were more important than the acid strength and acid sites of the studied MOFs, in terms of the referred catalytic performance. Finally, the reaction conditions were also shown to play an important role in the catalytic performance of the studied systems. Especially, the type of oxidant and the way to supply it to the reaction medium influenced the catalytic results.

Influence of the channel size of isostructural 3d–4f MOFs on the catalytic aerobic oxidation of cycloalkenes

The present work reports a new group of heterogeneous catalysts with a 3D structure, CuLnIDA, {[Cu₃Ln₂(IDA)₆]·8H₂O} (Ln: La^III, Gd^III or Yb^III), with an organic linker (H₂IDA: iminodiacetic acid).

Co-crystal structure of a dinuclear (Zn-Y) and a trinuclear (Zn-Y-Zn) complexes derived from a Schiff base ligand

The present investigation describes the synthesis and structural study of a metal-zinc ligand [ZnL.H2O], which was used to generate three dimensional supramolecular complex formulated as [Y{Zn(L)(SCN)}(SCN)2].[Y{Zn(L)(SCN)}2(DMF)2].(NO3). The title compound crystallizes in the triclinic space group P-1 with the following unit cell parameters: a = 14.8987(7) Å, b = 15.6725(8) Å, c = 19.2339(10) Å, a = 94.610(4)°, β = 103.857(4)°, γ = 101.473(4)°, V = 4234.4(4) Å3, Z = 2, R1 = 0.063 and wR2 = 0.96. For this compound, the structure reveals that one heterodinuclear unit [Y{Zn(L)(SCN)}(SCN)2] is co-crystallized with a heterotrinuclear unit [Y{Zn(L)(SCN)}2(DMF)2].(NO3). In the dinuclear moiety, the organic molecule acts as a hexadentate ligand and in the trinuclear unit, it acts as a pentadentate ligand with one of the oxygen methoxy group remaining uncoordinated. In both units the coordination environment of the zinc metal can be described as distorted square pyramidal. In the dinuclear unit the Y(III) is hexacoordinated while it is octacoordinated in the trinuclear unit. The environment of the Y(III) can be described as a distorted octahedral geometry in the dinuclear and as a distorted square antiprism in the trinuclear units respectively.

A Series of Robust Copper-Based Triazolyl Isophthalate MOFs: Impact of Linker Functionalization on Gas Sorption and Catalytic Activity †

The synthesis and characterization of an isomorphous series of copper-containing microporous metal-organic frameworks (MOFs) based on triazolyl isophthalate linkers with the general formula ∞3[Cu₄(μ₃-OH)₂(R¹-R²-trz-ia)₃(H₂O)_x] are presented. Through size adjustment of the alkyl substituents R¹ and/or R² at the linker, the impact of linker functionalization on structure-property relationships was studied. Due to the arrangement of the substituents towards the cavities, the porosity (pore fraction 28%–39%), as well as the pore size can be adjusted by the size of the substituents of the triazole ring. Thermal analysis and temperature-dependent PXRD studies reveal a thermal stability of the MOFs up to 230 °C due to increasing framework stability through fine-tuning of the linker substitution pattern. Adsorption of CO₂ (298 K) shows a decreasing maximum loading with increasing steric demand of the substituents of the triazole ring. Furthermore, the selective oxidation of cyclohexene with tert-butyl hydroperoxide (TBHP) is studied over the MOFs at 323 K in liquid chloroform. The catalytic activity increases with the steric demand of the substituents. Additionally, these isomorphous MOFs exhibit considerable robustness under oxidizing conditions confirmed by CO₂ adsorption studies, as well as by the catalytic selective oxidation experiments.

{[Cu3Lu2(ODA)6(H2O)6]·10H2O}n: the first heterometallic framework based on copper(ii)/lutetium(iii) for the catalytic oxidation of olefins and aromatic benzylic substrates

The catalytic performance of the novel framework {[Cu₃Lu₂(ODA)₆(H₂O)₆]·10H₂O}_n was tested in the oxidation of alkenes and benzylic hydrocarbons, using tert-butyl hydroperoxide (TBHP) and molecular oxygen (O₂) as oxidants.

Hybrid compounds assembled from copper-triazole complexes and phosphomolybdic acid as advanced catalysts for the oxidation of olefins with oxygen

Hybrid compounds of [CuI4(3atrz)₄][PMoVI11Mo^VO₄₀] (1) and [CuI6(3atrz)₆][PMo₁₂O₄₀]₂ (2) are active catalysts for olefin oxidation.

Ferrocene particles incorporated into Zr-based metal–organic frameworks for selective phenol hydroxylation to dihydroxybenzenes

Ferrocene@UiO-66 exhibited high catalytic activity for phenol hydroxylation with H₂O₂ at room temperature in water.