Post‐Synthetic Modification of Metal‐Organic Frameworks Bearing Phenazine Radical Cations for aza‐Diels‐Alder Reactions

Abstract

Metal-organic frameworks (MOFs) consisting of organic radicals are of great interest because they have exhibited unique and intriguing optical, electronic, magnetic, and chemo-catalytic properties, and thus have demonstrated great potential applications in optical, electronic, and magnetic devices, and as catalysts. However, the preparation of MOFs bearing stable organic radicals is very challenging because most organic radicals are highly reactive and difficult to incorporate into the framework of MOFs. Herein we reported a post-synthetic modification strategy to prepare a novel MOF containing phenazine radical cations, which was used as heterogeneous catalyst for aza-Diels-Alder reaction. The zinc-based metal-organic framework Zn 2 (PHZ) 2 (dabco) (N) was successfully synthesized from 5,10-di(4-benzoic acid)-5,10-dihydrophenazine (PHZ), triethylene diamine (dabco) with Zn(NO 3 ) 2 • 6H 2 O by solvothermal method. The as-synthesized MOF N was partially oxidized by AgSbF 6 to form MOF R containing ~10% phenazine radical cation species. The resultant MOF R was found to keep the original crystal type of N and very persistent under ambient conditions. Consequently, MOF R was successfully employed in radical cation-catalyzed aza-Diels-Alder reactions with various imine substrates at room temperature with high reaction conversion. Moreover, heterogeneous catalyst MOF R was reusable up to five times without much loss of catalytic activity, demonstrating its excellent stability and recyclability. Therefore, the post-synthetic modification developed in this work is expected to become a versatile strategy to prepare radicalbased MOFs for the application of heterogeneous catalysts in organic synthesis.

Leaching in Specific Facets of ZIF-67 and ZIF-L Zeolitic Imidazolate Frameworks During the CO2 Cycloaddition with Epichlorohydrin

“…This generates acidic Lewis centers. These materials have been used in epoxidation, , Diels-Alder, or CO 2 cycloaddition reactions with epoxides …”

“…This generates acidic Lewis centers. These materials have been used in epoxidation, 8,9 Diels-Alder, 10 or CO 2 cycloaddition reactions with epoxides. 11 For CO 2 cycloaddition (see Scheme 1), it is generally accepted that the Lewis acid sites are the active ones: 12 the epoxide first binds to the Lewis acid via basic oxygen donation, followed by a nucleophilic attack by the co-catalyst to activate the epoxide.…”

Self-assembly of conformation-adaptive dihydrophenazine-based coordination cages

“…Dihydrophenazine is a versatile class of nitrogen-containing electron-rich heterocycles, featuring a substantial conjugation, redox-active properties and conformation-adaptive behaviour. 1–7 Dihydrophenazine derivatives present tremendous chemical diversity and exhibit outstanding photochemical, electrochemical, and magnetic properties. 8–15 As a consequence, they have been widely used in the field of photocatalysis, batteries, luminescent materials, single molecule magnets, and other fields.…”

Host–Guest Encapsulation to Promote the Formation of a Multicomponent Trigonal-Prismatic Metallacage

“…1,2 The constructed SCCs possess elaborate architectures with well-defined shapes and sizes and can be easily functionalized through pre-or postmodification strategies. 3 The varied SCCs not only show aesthetic structural diversity but also have significant applications in a wide range of fields, such as host−guest recognition, 4 chemical sensors, 5 supramolecular polymers, 6 nanorotors, 7 catalysis, 8 and biomedicine. 9 Among them, the host−guest complexation of metallacages with aromatic hydrocarbons is one of the most attractive findings; these demonstrate unique photophysical or electroconductive properties and can be utilized for selective molecular sensing, separation of aromatic compounds, light harvesting, and catalysis.…”

“…In a typical coordination-driven self-assembly, at least one of the selected metal and organic building blocks has a convergent structural feature to allow the formation of discrete supramolecular coordination complexes (SCCs) . Rational design and careful control of the coordination mode make it possible to prepare various discrete metallosupramolecules, especially metal–organic cycles/cages (MOCs). , The constructed SCCs possess elaborate architectures with well-defined shapes and sizes and can be easily functionalized through pre- or postmodification strategies . The varied SCCs not only show aesthetic structural diversity but also have significant applications in a wide range of fields, such as host–guest recognition, chemical sensors, supramolecular polymers, nanorotors, catalysis, and biomedicine .…”