Highly Stable Mesoporous Zirconium Porphyrinic Frameworks with Distinct Flexibility

Topology Prediction of Gas-Separating Metal-Organic Frameworks with Low Symmetry Vertices

Topology serves as a blueprint for the construction of reticular structures such as metal-organic frameworks, especially for those based on building blocks with highly symmetrical shapes. However, it remains a challenge to predict the topology of the frameworks from less symmetrical units, because their corresponding vertex figures are largely deformed from the perfect geometries with no "default" net embedding. Furthermore, vertices involving flexible units may have multiple shape choices, and the competition among their designated topologies makes the structure prediction in large uncertainty. Herein, the deformation index is proposed to characterize the symmetry loss of the vertex figure by comparing it with its ideal geometry. The mathematical index is employed to predict the shapes of two in situ formed Co-based metalloligands (pseudo-tetrahedron and pseudo-square), which further dictate the framework topology (flu and scu) when they are joined with the [Zr6O8]-based cuboid units. The two frameworks with very similar constituents provide an ideal platform to investigate how the pore shapes and interconnectivity influence the gas separation. The net with cylindrical channels outperforms the other with discreate cages in C3H8/C2H6/CH4 separation, benefiting from the facile accessibility of its interaction sites to the guests imposed by the specific framework topology.

Traceless Benzylic C-H Amination via Bifunctional N-Aminopyridinium Intermediates

C-H amination reactions provide the opportunity to streamline the synthesis of nitrogen-containing organic small molecules. The impact of intermolecular C-H amination methods, however, is currently limited the frequent requirement for the amine precursors to bear activating groups, such as N-sulfonyl substituents, that are both challenging to remove and not useful synthetic handles for subsequent derivatization. Here, we introduce traceless nitrogen activation for C-H amination-which enables application of selective C-H amination chemistry to the preparation of diverse N-functionalized products-via sequential benzylic C-H N-aminopyridylation followed by Ni-catalyzed C-N cross-coupling with aryl boronic acids. Unlike many C-H amination reactions that provide access to protected amines, the current method installs an easily diversifiable synthetic handle that serves as a lynchpin for C-H amination, deaminative N-N functionalization sequences.

Porphyrin and phthalocyanine-based metal organic frameworks beyond metal-carboxylates

Given the ubiquitous role of porphyrins in natural systems, these molecules and related derivatives such as phthalocyanines are fascinating building units to achieve functional porous materials. Porphyrin-based MOFs have been developed over the past three decades, yet chemically robust frameworks, necessary for applications, have been achieved much more recently and this field is expanding. This progress is partially driven by the development of porphyrins and phthalocyanines bearing alternative coordinating groups (phosphonate, azolates, phenolates…) that allowed moving the related MOFs beyond metal-carboxylates and achieving new topologies and properties. In this perspective article we first give a brief outline of the synthetic pathways towards simple porphyrins and phthalocyanines bearing these complexing groups. The related MOF compounds are then described; their structural and textural properties are discussed, as well as their stability and physical properties. An overview of the resulting nets and topologies is proposed, showing both the similarities with metal-carboxylate phases and the peculiarities related to the alternative coordinating groups. Eventually, the opportunities offered by this recent research topic, in terms of both synthesis pathways and modulation of pore size and shape, stability and physical properties, are discussed.

Transient Catenation in a Zirconium-Based Metal-Organic Framework and Its Effect on Mechanical Stability and Sorption Properties

Interpenetration of two or more sublattices is common among many metal-organic frameworks (MOFs). Herein, we study the evolution of one zirconium cluster-based, 3,8-connected MOF from its non-interpenetrated (NU-1200) to interpenetrated (STA-26) isomer. We observe this transient catenation process indirectly using ensemble methods, such as nitrogen porosimetry and X-ray diffraction, and directly, using high-resolution transmission electron microscopy. The approach detailed here will serve as a template for other researchers to monitor the interpenetration of their MOF samples at the bulk and single-particle limits. We investigate the mechanical stability of both lattices experimentally by pressurized in situ X-ray diffraction and nanoindentation as well as computationally with density functional theory calculations. Both lines of study reveal that STA-26 is considerably more mechanically stable than NU-1200. We conclude this study by demonstrating the potential of these MOFs and their mixed phases for the capture of gaseous n-hexane, used as a structural mimic for the chemical warfare agent sulfur mustard gas.

Improving MOF stability: approaches and applications

This review summarizes recent advances in the design and synthesis of stable MOFs and highlights the relationships between the stability and functional applications.

Metal–organic frameworks (MOFs) have been recognized as one of the most important classes of porous materials due to their unique attributes and chemical versatility. Unfortunately, some MOFs suffer from the drawback of relatively poor stability, which would limit their practical applications. In the recent past, great efforts have been invested in developing strategies to improve the stability of MOFs. In general, stable MOFs possess potential toward a broader range of applications. In this review, we summarize recent advances in the design and synthesis of stable MOFs and MOF-based materials via de novo synthesis and/or post-synthetic structural processing. Also, the relationships between the stability and functional applications of MOFs are highlighted, and finally, the subsisting challenges and the directions that future research in this field may take have been indicated.

A series of robust metal-porphyrinic frameworks based on rare earth clusters and their application in N-H carbene insertion

We herein report a series of microporous metal-porphyrinic frameworks (MPFs), denoted as NUPF-2M, based on rare earth (RE) clusters. NUPF-2M represent the first examples of RE cluster-based MPFs, possessing a rarely seen shp-a topology and exhibiting high thermal and thermal stabilities. After a post-metallization process with FeCl₃, NUPF-2M is catalytically active as an efficient heterogeneous catalyst for intermolecular N-H carbene insertion.

Stable metal–organic frameworks as a host platform for catalysis and biomimetics

Recent years have witnessed the exploration and synthesis of an increasing number of metal–organic frameworks (MOFs). The utilization of stable MOFs as a platform for catalysis and biomimetics is discussed.

Carbene insertion into N–H bonds with size-selectivity induced by a microporous ruthenium–porphyrin metal–organic framework

A stable and porous porphyrinic metal–organic framework Ru-PMOF-1(Hf) has been prepared and used for N–H insertion reactions with high efficiency and selectivity.

Transition-Metal Phosphide-Carbon Nanosheet Composites Derived from Two-Dimensional Metal-Organic Frameworks for Highly Efficient Electrocatalytic Water-Splitting

The preparation of highly active, sustainable, nonprecious metal materials as hydrogen evolution and oxygen evolution reaction (HER and OER) catalysts that can relieve the environmental pollution and energy shortage problems present a great challenge to chemists. We herein report the fabrication of a highly active metal phosphide-carbon composite catalyst for HER and OER in acid and basic solution, respectively. The catalyst is derived through carbonization and subsequent phosphorization of two-dimensional (2D) cobalt porphyrinic metal-organic framework nanosheets. It consists of cobalt phosphide nanoparticles embedded in mesoporous N-doped graphitic carbon materials. The catalyst shows good electrocatalytic activities for HER in 0.5 M H₂SO₄ and OER in 1 M KOH with overpotentials of 98 and 370 mV at a current density of 10 mA cm^-2 and the Tafel slopes of 74 and 79 mV dec^-1, respectively. In addition, the catalyst also shows good durability. The method used in this study could be applied to prepare new, highly efficient water-splitting catalysts by using diverse 2D metal-organic frameworks as templates.

A robust indium–porphyrin framework for CO2 capture and chemical transformation

A robust indium–porphyrin framework based on amido-decorated porphyrin ligands is used for CO₂ capture and chemical fixation, showing good catalytic activity and recyclability.