Bifunctional Noble-Metal-Free Catalyst for the Selective Aerobic Oxidation-Knoevenagel One-Pot Reaction: Encapsulation of Polyoxometalates into an Alkylamine-Modified MIL-101 Framework

Abstract

One-pot reactions offer economic and environmental advantages. Therefore, the design and synthesis of multifunctional catalysts capable of catalyzing multistep organic transformations are highly important. Herein, an effective bifunctional heterogeneous catalyst is presented. For the first time, the encapsulation of H5PMo10V2O40 (PMoV2) polyoxometalate into the cages of an alkylamine-modified MIL-101 using an optimized double-solvent method is reported. The obtained PMoV2@DETA-MIL-101 material displays a great catalytic performance (99% conversion of alcohols) for the selective aerobic oxidation-Knoevenagel one-pot reaction. To the best of our knowledge, this is one of the first reports on the usage of noble-metal-free catalysts for the aerobic oxidation-Knoevenagel one-pot reaction without the addition of additives. The catalyst is very stable and can be used for at least five cycles with no leaching of the active sites.

Polyoxometalate‐based Inorganic‐Organic Hybrids as Heterogeneous Catalysts for Asymmetric and Tandem Reactions

“…However, PMoV 2 @DETA-MIL-101 enabled this tandem reaction without the need of noble metal catalysts or base additives. [73] Li et al prepared MOF-808 and encapsulated Keggin-type H 3 PW 12 O 40 into that to generate HPW@MOF-808 catalyst for tandem transformation of levulinic acid to γ-valerolactone. To prepare the catalyst, MOF-808 was solvothermally synthesized in DMF using ZrOCl 2 .8H 2 O, 1,3,5-benzene tricarboxylic acid and formic acid.…”

“…The results showed that benzyl alcohol was selectively converted to benzylidene malononitrile after 36 h. An aerobic oxidation of alcohols to aldehydes followed by the Knoevenagel condensation has been reported using either noble metal catalysts or noble‐free metal catalysts in the presence of a base additive. However, PMoV 2 @DETA‐MIL‐101 enabled this tandem reaction without the need of noble metal catalysts or base additives [73] …”

A highly robust cluster-based indium(iii)–organic framework with efficient catalytic activity in cycloaddition of CO2 and Knoevenagel condensation

“…† As shown in entries 2-4 of Table 4, the high yields were achieved from benzaldehydes with electron-withdrawing groups (-NO 2 , -F and -Br), which could effectively reduce the electron density around the CvO group. [70][71][72][73] In contrast, benzaldehyde derivatives with electron-donating groups (-CH 3 ) had a certain blocking effect on the conversion process, which slightly reduces the yield (entries 5 and 6, Table 4). In addition, entries 6 and 7 exhibit that the significantly decreased yields of 2-((3,4-dimethoxyphenyl)methylene)propanedinitrile and 2-((3,4,5-trimethoxyphenyl)methylene)propanedinitrile should be attributed to the large molecular size of the substrates, which greatly affected the large-scale diffusion of molecules in channels and the efficient contact with active sites.…”

A Porphyrin-Based Covalent Organic Framework as Metal-Free Visible-LED-Light Photocatalyst for One-Pot Tandem Benzyl Alcohol Oxidation/Knoevenagel Condensation

“…Tandem reactions usually require multifunctional catalysts that are able to promote more than one single reaction [ 30 ]. The formation of a carbon–carbon bond through the selective aerobic oxidation of alcohols and consecutive Knoevenagel condensation reaction is one of the most fundamental transformations in organic chemistry [ 31 , 32 , 33 , 34 ]. In this context, various heterogeneous catalysts have been reported but possess numerous shortcomings, including poor stability, precious metals, and/or metal contamination, thereby hampering their practical applications [ 7 , 8 , 35 , 36 ].…”