Synthesis of Metal-Organic Cages via Orthogonal Bond Cleavage in 3D Metal-Organic Frameworks.

Herein we address the question of whether a supramolecular finite metal-organic structure such as a cage or metal-organic polyhedron (MOP) can be synthesized via controlled cleavage of a three-dimensional (3D) metal-organic structure. To demonstrate this, we report the synthesis of a Cu(II)-based cuboctahedral MOP through orthogonal olefinic bond cleavage of the cavities of a 3D, Cu(II)-based, metal-organic framework (MOF). Additionally, we demonstrate that controlling the ozonolysis conditions used for the cleavage enables Clip-off Chemistry synthesis of two cuboctahedral MOPs that differ by their external functionalization: one in which all 24 external groups represent a mixture of aldehydes, carboxylic acids, acetals and esters, and one in which all are aldehydes.

Isolation of the Secondary Building Unit of a 3D Metal-Organic Framework through Clip-Off Chemistry, and Its Reuse To Synthesize New Frameworks by Dynamic Covalent Chemistry.

Herein, we present a novel methodology for synthesizing metal clusters or secondary building units (SBUs) that are subsequently employed to construct innovative metal-organic frameworks (MOFs) via dynamic covalent chemistry. Our approach entails extraction of SBUs from preformed MOFs through complete disassembly by clip-off chemistry. The initial MOF precursor is designed to incorporate the desired SBU, connected exclusively by cleavable linkers (in this study, with olefinic bonds). Cleavage of all the organic linkers (in this study, via ozonolysis under reductive conditions) liberates the SBUs functionalized with aldehyde groups. Once synthesized, these SBUs can be further reacted with amines in dynamic covalent chemistry to build new, rationally designed MOFs.

Unveiling Hidden Zeolitic Imidazolate Frameworks Guided by Intuition-Based Geometrical Factors.

Herein, synthesizable candidate topologies to form zeolitic imidazolate frameworks (ZIFs) are efficiently identified from over 2 000 000 hypothetical structures in zeolite databases, using structural descriptors extracted from known ZIFs. A combination of intuition-based structural descriptors, such as ring patterns, node numbers, and TOT bridging angles (T = tetrahedral metal nodes in zeolites and ZIFs), is used as data filters to eliminate topologies infeasible for ZIF formation. Carefully chosen structural descriptors facilitate the prediction of plausible ZIF topologies. To investigate potential applications as porous ZIFs, this work performs hydrogen adsorption screening and suggested notable target ZIFs. The collection of new plausible ZIFs, derived from the combined descriptors, will be a structural blueprint for synthetic chemists.

The rise of metal-organic polyhedra.

Metal-organic polyhedra are a member of metal-organic materials, and are together with metal-organic frameworks utilized as emerging porous platforms for numerous applications in energy- and bio-related sciences. However, metal-organic polyhedra have been significantly underexplored, unlike their metal-organic framework counterparts. In this review, we will cover the topologies and the classification of metal-organic polyhedra and share several suggestions, which might be useful to synthetic chemists regarding the future directions in this rapid-growing field.

Role of Zr6 Metal Nodes in Zr-Based Metal-Organic Frameworks for Catalytic Detoxification of Pesticides.

Pesticides are chemicals widely used for agricultural industry, despite their negative impact on health and environment. Although various methods have been developed for pesticide degradation to remedy such adverse effects, conventional materials often take hours to days for complete decomposition and are difficult to recycle. Here, we demonstrate the rapid degradation of organophosphate pesticides with a Zr-based metal-organic framework (MOF), showing complete degradation within 15 min. MOFs with different active site structures (Zr node connectivity and geometry) were compared, and a porphyrin-based MOF with six-connected Zr nodes showed remarkable degradation efficiency with half-lives of a few minutes. Such a high efficiency was further confirmed in a simple flow system for several cycles. This study reveals that MOFs can be highly potent heterogeneous catalysts for organophosphate pesticide degradation, suggesting that coordination geometry of the Zr node significantly influences the catalytic activity.

Chemo- and regioselective click reactions through nickel-catalyzed azide-alkyne cycloaddition.

Metal-catalyzed cycloaddition is an expeditious synthetic route to functionalized heterocyclic frameworks. However, achieving reactivity-controlled metal-catalyzed azide-alkyne cycloadditions from competing internal alkynes has been challenging. Herein, we report a nickel-catalyzed [3 + 2] cycloaddition of unsymmetrical alkynes with organic azides to afford functionalized 1,2,3-triazoles with excellent regio- and chemoselectivity control. Terminal alkynes and cyanoalkynes afford 1,5-disubstituted triazoles and 1,4,5-trisubstituted triazoles bearing a 4-cyano substituent, respectively. Thioalkynes and ynamides exhibit inverse regioselectivity compared with terminal alkynes and cyanoalkynes, affording 1,4,5-trisubstituted triazoles with 5-thiol and 5-amide substituents, respectively. Density functional theory calculations are performed for the elucidation of the reaction mechanism. The computed mechanism suggests that a nickellacyclopropene intermediate is generated by the oxidative addition of the alkyne substrate to the Ni(0)-Xantphos catalyst, and the subsequent C-N coupling of this intermediate with an azide is responsible for the chemo- and regioselectivity.

Chemoselective Trifluoroethylation Reactions of Quinazolinones and Identification of Photostability.

Herein, we report chemoselective trifluoroethylation routes of unmasked 2-arylquinazolin-4(3 H)-ones using mesityl(2,2,2-trifluoroethyl)iodonium triflate at room temperature. Homologous C-, O-, and N-functionalized subclasses are accessed in a straightforward manner with a wide substrate scope. These chemoselective branching events are driven by Pd-catalyzed ortho-selective C-H activation at the pendant aryl ring and base-promoted reactivity modulation of the amide group, leveraging the intrinsic directing capability and competing pronucleophilicity of the quinazolin-4(3 H)-one framework. Furthermore, outstanding photostability of the quinazolin-4(3 H)-one family associated with nonradiative decay is presented.

Molecular Engineered Safer Organic Battery through the Incorporation of Flame Retarding Organophosphonate Moiety.

Here, we report the first electrochemical assessment of organophosphonate-based compound as a safe electrode material for lithium-ion batteries, which highlights the reversible redox activity and inherent flame retarding property. Dinickel 1,4-benzenediphosphonate delivers a high reversible capacity of 585 mA h g-1 with stable cycle performance. It expands the scope of organic batteries, which have been mainly dominated by the organic carbonyl family to date. The redox chemistry is elucidated by X-ray absorption spectroscopy and solid-state 31P NMR investigations. Differential scanning calorimetry profiles of the lithiated electrode material exhibit suppressed heat release, delayed onset temperature, and endothermic behavior in the elevated temperature zone.

Cross-linking Zr-based metal-organic polyhedra via postsynthetic polymerization.

Metal organic polyhedra (MOPs) have potential as supramolecular building blocks, but utilizing MOPs for postsynthetic polymerization has not been explored. Although MOPs with flexible organic moieties have been recently reported to target enhanced processability, permanent porosity has not been demonstrated. Here, a novel synthetic strategy involving the cross-linking of MOPs via a covalent bond is demonstrated by exploiting a condensation reaction between the MOP and flexible organic linkers. An amine-functionalized Zr-based MOP is cross-linked with acyl chloride linkers in the crystalline state to form cross-linked MOPs. The condensation reaction results in a cross-linked system without significant changes to the structure of the Zr-based MOP. Such cross-linked MOPs provide a microporous tetrahedral cage based on gas sorption analysis. This cross-linking strategy highlights the potential of MOPs as building blocks and provides access to a new class of porous material.