Atomically Precise Crystalline Materials Based on Kinetically Inert Metal Ions via Reticular Mechanopolymerization

Generic and facile mechanochemical access to versatile lattice-confined Pd(ii)-based heterometallic sites

Metal-organic frameworks (MOFs) show remarkable potential in a broad array of applications given their physical and chemical versatility. Classical synthesis of MOFs is performed using solution chemistry at elevated temperatures to achieve reversible metal-ligand bond formation. These harsh conditions may not be suitable for chemical species sensitive to high temperature or prone to deleterious reactions with solvents. For instance, Pd(ii) is susceptible to reduction under solvothermal conditions and is not a common metal node of MOFs. We report a generic and facile mechanochemical strategy that directly incorporates a series of Pd(ii)-based heterobimetallic clusters into MOFs as metal nodes without Pd(ii) being reduced to Pd(0). Mechanochemistry features advantages of short reaction time, minimum solvent, high reaction yield, and high degree of synthetic control. Catalytic performances of lattice-confined heterobimetallic sites are examined for nitrene transfer reactions and we demonstrate that the chemoselectivity for allylic amination versus olefin aziridination is readily tuned by the identity of the first-row metal ion in Pd(ii)-based heterobimetallic clusters.

Facile mechanochemical synthesis of MIL-53 and its isoreticular analogues with a glance at reaction reversibility

MIL-53 represents one of the most notable metal-organic frameworks given its unique structural flexibility and remarkable thermal stability. In this study, a shaker-type ball milling method has been developed into a facile and generalizable synthetic strategy to access a family of MIL-53 type materials under ambient conditions. During the explorations of [M(OH)(fumarate)] (M = Al, Ga, and In), we report a positive correlation between the metal-ligand (M-L) bond reversibility and the size of resultant crystallites under the mechanochemical process. The more kinetically labile the M-L bond is, the larger the afforded crystallite size is.

Mechanochemical Access to Catechol-Derived Metal-Organic Frameworks

Mechanochemistry, a resurging synthetic approach, has been developed into an effective and controllable method to access a family of crystalline porous catechol-derived metal-organic frameworks (MOFs) for the first time. We have identified that the obtained crystalline phase is readily tunable by precursors and the addition of solvents or drying agents. The described mechanochemistry allows us to synthesize these materials in a highly sustainable manner. Thus, mechanochemistry is expected to pave a promising avenue to access a broader class of MOF materials, in addition to those based on the motifs of carboxylic acid or imidazole.

Multicomponent, Functionalized HKUST-1 Analogues Assembled via Reticulation of Prefabricated Metal-Organic Polyhedral Cavities

Metal–organic frameworks (MOFs) assembled from multiple building blocks exhibit greater chemical complexity and superior functionality in practical applications. Herein, we report a new approach based on using prefabricated cavities to design isoreticular multicomponent MOFs from a known parent MOF. We demonstrate this concept with the formation of multicomponent HKUST-1 analogues, using a prefabricated cavity that comprises a cuboctahedral Rh(II) metal–organic polyhedron functionalized with 24 carboxylic acid groups. The cavities are reticulated in three dimensions via Cu(II)-paddlewheel clusters and (functionalized) 1,3,5-benzenetricarboxylate linkers to form three- and four-component HKUST-1 analogues.

Linking metal-organic cages pairwise as a design approach for assembling multivariate crystalline materials

Using metal-organic cages (MOCs) as preformed supermolecular building-blocks (SBBs) is a powerful strategy to design functional metal-organic frameworks (MOFs) with control over the pore architecture and connectivity. However, introducing chemical complexity into the network via this route is limited as most methodologies focus on only one type of MOC as the building-block. Herein we present the pairwise linking of MOCs as a design approach to introduce defined chemical complexity into porous materials. Our methodology exploits preferential Rh-aniline coordination and stoichiometric control to rationally link Cu4L4 and Rh4L4 MOCs into chemically complex, yet extremely well-defined crystalline solids. This strategy is expected to open up significant new possibilities to design bespoke multi-functional materials with atomistic control over the location and ordering of chemical functionalities.

Mechanochemistry of Group 4 Element-Based Metal-Organic Frameworks

Mechanochemical synthesis is emerging as an environmentally friendly yet efficient approach to preparing metal-organic frameworks (MOFs). Herein, we report our systematic investigation on the mechanochemical syntheses of Group 4 element-based MOFs. The developed mechanochemistry allows us to synthesize a family of Hf₄O₄(OH)₄(OOC)₁₂-based MOFs. Integrating [Zr₆O₄(OH)₄(OAc)₁₂]₂ and [Hf₆O₄(OH)₄(OAc)₁₂]₂ under the mechanochemical conditions leads to a unique family of cluster-precise multimetallic MOFs that cannot be accessed by the conventional solvothermal synthesis. Extensive efforts have not yielded an effective pathway for preparing Ti^IV-derived MOFs, tentatively because of the relatively low Ti-O bond dissociation energy.

A Fast and Convenient Synthesis of New Water-Soluble, Polyanionic Dendrimers

Reasonably simple, efficient, and possessing aspects of generality, the methodology for the synthesis of new, water-soluble, dendrimeric polyesters with great potential applications as antiviral drugs in their own right is described. The essential aspect of the presented approach is a quite unique, immediate access to the polyanionic material at each generation during divergent synthesis. Six target polyanionic dendrimers (generations 1, 2, and 3) have been synthesized. The key monomers applied in this project were 1,3,5-benzenetricarboxylic acid derivatives, which also worked as direct precursors of the charged dendrimer surface.

Synthesis of atomically precise single-crystalline Ru2-based coordination polymers

Methods to incorporate kinetically inert metal nodes and highly basic ligands into single-crystalline metal-organic frameworks (MOFs) are scarce, which prevents synthesis and systematic variation of many potential heterogeneous catalyst materials. Here we demonstrate that metallopolymerization of kinetically inert Ru2 metallomonomers via labile Ag-N bonds provides access to a family of atomically precise single-crystalline Ru2-based coordination polymers with varied network topology and primary coordination sphere.

Porous metal-organic alloys based on soluble coordination cages

Diverse strategies for the preparation of mixed-metal three-dimensional porous solids abound, although many of them lend themselves only moderate levels of tunability. Herein, we report the design and synthesis of surface functionalized permanently microporous coordination cages and their use in the isolation of mixed metal solids. Judicious alkoxide-based ligand functionalization was utilized to tune the solubility of starting copper(ii)-based cages and their resulting compatibility with the mixed-cage approach described here. We further prepared a family of isostructural molybdenum(ii) cages for a subset of the ligands. The preparation of mixed-metal cage solids proceeds under facile conditions where solutions of parent cages are mixed and product phases isolated. A suite of spectroscopic and characterization tools confirm the starting cages are intact in the amorphous product. Finally, we show that utilization of precise ligand functional groups can be used to prepare mixed cage solids that can be easily and cleanly separated into their constituent components through simple solvent washing or solvent extraction techniques.