This Concept paper summarizes the recent advances in metal-organic framework (MOF) based hydrogen atom transfer catalysis. Design principles, effects and advantages of MOF platform, and current limitations are discussed.

Abstract

This concept paper aims to summarize recent research on the design and synthetic applications of metal-organic frameworks (MOFs)-based hydrogen atom transfer (HAT) catalysts. Functional MOFs have emerged as highly promising heterogeneous catalysts, leveraging their tunable, ordered structure and abundant active sites to enhance catalytic efficiency in various reactions. HAT, a versatile method for generating active open-shell radical species through selective hydrogen abstraction, has been well explored in homogeneous photocatalysis. In contrast, heterogeneous HAT catalysis remains less developed, albeit their great potential in industry. This paper will provide a timely overview of the advancements in MOFs-based HAT photocatalysis, classified according to catalytic centers including aromatic ketones, polyoxometalates, xanthene dyes, thiols, and alcohols, highlighting their design principles and practical applications in photocatalytic organic synthesis.

Polyoxometalate-based frameworks, as a kind of material combined both the advantages of oxygen-rich polyoxometalates (POMs) and porous metal-organic frameworks (MOFs) within one single system, could serve as potential photocatalysts with diverse structure features. This review focus on the recent development based on the POM-based frameworks along with their construction strategies and applications in various areas of photocatalysis, mainly including water splitting, CO₂ reduction, organic synthesis and also the selective coupling reactions.

Abstract

Polyoxometalate-based frameworks, as a kind of material constructed by polyoxometalates (POMs), metal ions or clusters, organic ligands, are combined both the advantages of oxygen-rich POMs and porous metal-organic frameworks (MOFs) within one single system. This integration greatly expands their potential applications compared to the individual POMs or MOFs. Particularly for photocatalysis, the narrow light absorption range of the typical POMs units in the ultraviolet region hinders their extensive uses as visible-light-driven photocatalysts. However, the incorporation of photoactive units into POMs-based frameworks can be considered as an effective approach to overcome this limitation. In this paper, we review selected examples of recent progress based on the POM-based frameworks along with their construction strategies and applications in various areas of photocatalysis, mainly including water splitting, CO₂ reduction, organic synthesis and also the selective coupling reactions.

The effects of oxygen functionalities on GNP (Graphene Nanoplatelets) has been investigated, functionalizing GNP in liquid phase using different oxidants (HNO₃, H₂O₂, KMnO₄), with the aim to tune the amount and the type of oxygen functionalities. Pd NPs have been deposited on the different functionalized carbon supports to be tested in benzaldehyde hydrogenation/hydrogenolysis to benzyl alcohol and toluene as model reaction.

Abstract

This paper presents a study on the effects of oxygen functionalities on a mesoporous and graphitized carbon support (GNP, Graphene Nanoplatelets), on the catalytic activity of Pd/GNP catalysts in hydrogenation reactions. A functionalization method in liquid phase has been employed, using different oxidants (HNO₃, H₂O₂, KMnO₄), with the aim to tune the amount and the type of introduced oxygen functionalities. Preformed Pd nanoparticles have been used as Pd-precursor to limit differences in metal particle size and dispersion on differently functionalized carbon. The catalytic behaviour in benzaldehyde hydrogenation/hydrogenolysis to benzyl alcohol and toluene revealed that the introduction of oxygen functionalities has a generally detrimental effect. NMR relaxometry studies highlighted the weaker interaction between the carbonyl group and the functionalized Pd/GNP surface than the non–functionalized Pd/GNP demonstrating that the origin of the different catalytic activity lies on the first step of the reaction. O-functionalities also impacted on the Pd⁰/Pd²⁺ ratio at the surface which is an established parameter correlated to the reaction rate.

Small, strained carbocyclic systems have fascinated organic chemists from both a theoretical and synthetic standpoint. These systems often challenge conventional wisdom when it comes to molecular structure and tactics for chemical construction. The cyclopropyl motif is one such ring system that remains at the forefront of method development in the modern era. With the advent of an array of non-traditional building blocks, a range of new cyclopropanation processes using one- and two-electron strategies have been developed that not only overcome the synthetic shortcomings of classical approaches but also provide entry into a wide range of new classes of cyclopropanes. This review discusses recent advances in this area with an emphasis on their mechanistic underpinnings and potential applications. Additionally, a concise overview of the properties of and traditional approaches to cyclopropanes is provided.