A Green Alternative for the Direct Aerobic Iodination of Arenes Using Molecular Iodine and a POM@MOF Catalyst

Abstract

Iodoarenes are important precursors for fine chemicals and pharmaceuticals. The direct iodination of arenes using molecular iodine (I2) has emerged as an attractive green synthesis method. Most of the direct iodination protocols are still homogeneous systems that require harsh conditions and use or produce toxic products. We report a new heterogeneous catalytic route for the direct aerobic iodination of arenes under mild conditions using a PMoV2 polyoxometalate (POM) embedded in the metal–organic framework (MOF) MIL-101 (PMoV2@MIL-101). The catalyst shows full yield for the conversion of mesitylene to 2-iodomesitylene at a rate that is similar to the homogeneous POM system. Moreover, the catalyst is applicable for a wide range of substrates in an oxygen atmosphere without using any co-catalysts or sacrificial agents. To the best of our knowledge, this is the first report on designing a sustainable and green MOF-based heterogeneous catalytic system for the direct iodination reaction using molecular oxygen and iodine.

Elucidation of Active Sites and Mechanistic Pathways of a Heteropolyacid/Cu-Metal–Organic Framework Catalyst for Selective Oxidation of 5-Hydroxymethylfurfural via Ex Situ X-ray Absorption Spectroscopy and In Situ Attenuated Total Reflection-Infrared Studies

“…This phenomenon is one of the most significant factors behind the outstanding catalytic activity. 16,60,61 Additionally, the Raman spectra (Figure 7b) show distinct PMA characteristic peaks at 1002 cm −1 from the Cu-BTC_PMA composite. This phenomenon suggests that the Keggin-type structure is retained after incorporation of the PMA cluster into the MOF matrix.…”

“…The complete encapsulation of PMA inside the confined pore of the Cu-BTC MOF occurs which most likely accounts for the outstanding synergistic effect. This phenomenon is one of the most significant factors behind the outstanding catalytic activity. ,, …”

“…One promising pathway toward developing a suitable selective catalyst is the use of metal–organic frameworks (MOFs) due to their excellent properties including selective active sites and confined pores with a very high surface area. − The stability and oxidation property of the MOF can be enhanced by encapsulating active components such as highly oxidative polyoxometalates (POMs) in the confined MOF pore. , POMs (phosphomolybdic acid H 3 (PMo 12 O 40 ), tungstophosphoric acid, and silicotungstic acid) have an electronically diverse matrix, redox behavior, and various structural flexibility, and they can deliver themselves as an inorganic building block to forming an interaction with MOFs through various chemical bonding such as coordination or hydrogen bonding to accomplish very high stability of the composite material (PMA-incorporated MOF). , The extensive availability of the coordination modes of transition metals in MOFs can assist to generate the assembly of the polyoxometalate-incorporated MOF , which can achieve the unique structure due to the unprecedented synergistic interaction between polyoxometalate and MOF that directs to catalytic supremacy. In addition to that, the POM and MOF composite material exhibits a unique redox cycle between Mo +6 and Mo +5 and oxygen vacancy due to electronic synergistic interaction between the POM and MOF.…”

Highly oxidative desulfurization of thiophenic model fuels and real gasoline by Keggin‐type heteropolyanion immobilized on polyaniline and chitosan as an efficient organic–inorganic nanohybrid catalyst

“…Polyoxometalates (POMs) are a type of inorganic polyanionic clusters bearing well-defined topologic architecture comprised of early transition oxo-metalates and display excellent catalytic activity due to their acid-base and redox properties. [17][18][19][20][21] Nevertheless, due to high solubility, low surface area (close to 5 m 2 g À1 ), along with poor recovery, research has been developed by immobilizing POMs on a suitable support. [22][23][24][25][26][27] To overcome this limitation, polyaniline (PAN) and chitosan (CH) polymers were used as supports in the present study.…”

“…Many researchers have developed the design of brand‐new catalysts to attain high desulfurization in ODS. Polyoxometalates (POMs) are a type of inorganic polyanionic clusters bearing well‐defined topologic architecture comprised of early transition oxo‐metalates and display excellent catalytic activity due to their acid–base and redox properties 17–21 . Nevertheless, due to high solubility, low surface area (close to 5 m 2 g −1 ), along with poor recovery, research has been developed by immobilizing POMs on a suitable support 22–27 .…”