Chromium(III) Terephthalate Metal Organic Framework (MIL-101): HF-Free Synthesis, Structure, Polyoxometalate Composites, and Catalytic Properties

Abstract

Hybrid materials of the metal−organic framework (MOF), chromium(III) terephthalate (MIL-101), and phosphotungstic acid (PTA) were synthesized in aqueous media in the absence of hydrofluoric acid. XRD analysis of the MIL101/PTA composites indicates the presence of ordered PTA assemblies residing in both the large cages and small pores of MIL-101, which suggests the formation of previously undocumented structures. The MIL101/PTA structure enables a PTA payload 1.5−2 times higher than previously achieved. The catalytic performance of the MIL101/PTA composites was assessed in the Baeyer condensation of benzaldehyde and 2-naphthol, in the three-component condensation of benzaldehyde, 2-naphthol, and acetamide, and in the epoxidation of caryophyllene by hydrogen peroxide. The catalytic efficiency was demonstrated by the high (over 80−90%) conversion of the reactants under microwave-assisted heating. In four consecutive reaction cycles, the catalyst recovery was in excess of 75%, whereas the product yields were maintained above 92%. The simplicity of preparation, exceptional stability, and reactivity of the novel composites indicate potential in utilization of these catalytic matrices in a multitude of catalytic reactions and engineering processes.

Cr-MIL-101 encapsulated Keggin phosphotungstic acid as active nanomaterial for catalysing the alcoholysis of styrene oxide

“…2a However, it has been recently claimed by Hatton and coworkers that HPW can reside both in the large and the small cages of MIL-101. 20 In Figure 3b, all MIL-101 spectroscopic fingerprints in the 1200-700 cm -1 range are present. The highest frequency range (3850-2500 cm -1 ) shown in the inset, shows again many similarities between the MIL-101(H 2 O) and MIL-101(HPW) samples.…”

A magnetically-separable H 3 PW 12 O 40 @Fe 3 O 4 /EN-MIL-101 catalyst for the one-pot solventless synthesis of 2H-indazolo[2,1- b ] phthalazine-triones

“…MIL-101(Cr) was synthesized and purified according to the reported literature [45]. Briefly, 40 mL of deionized water was added to a mixture of ground, powdered terephthalic acid (1.66 g, 10 mmol) and Cr(NO3)3.9H2O (4.0 g, 10 mmol).…”

Influence of Strong Electronegativity Groups -Cl as the Adsorption Center of PTA@MIL-101-NH²-Cl for the Selective Hydrolysis of Cellulose into Glucose

“…1), indicating that the different TA -Cl / PTA samples have the MIL-101 type crystal structure, and the change of the graft amount of -Cl does not have obvious influence on the crystal structure of the synthesized sample. It can be seen from the Figure that each sample exhibits a diffraction peak due to the increase of the charge density of the crystal structure after loading PTA at 2θ = 7.6 o , indicating that PTA is successfully immobilized on the sample [22]. The PTA immobilization change of PTA@MIL-101-NH 2 -Cl after grafted -Cl was analyzed by FT-IR.…”