Anion Binding as a Strategy for the Synthesis of Porous Salts.

Porous salts have recently emerged as a promising new class of ultratunable permanently microporous solids. These adsorbents, which were first reported as ionic solids based on porous cations and anions, can be isolated from a wide variety of charged, permanently porous coordination cages. A challenge in realizing the full tunability of such systems, however, lies in the fact that the majority of coordination cages for which surface areas have been reported are comprised of charge-balanced inorganic and organic building blocks that result in neutral cages.

Utilization of a Mixed-Ligand Strategy to Tune the Properties of Cuboctahedral Porous Coordination Cages.

Ligand functionalization has been thoroughly leveraged to alter the properties of paddlewheel-based coordination cages where, in the case of ligand-terminated cages, functional groups are positioned on the periphery of synthesized cages. While these groups can be used to optimize solubility, porosity, crystal packing, thermal stability toward desolvation, reactivity, or optical activity, optimization of multiple properties can be challenging given their interconnected nature. For example, installation of functional groups to increase the solubility of porous cages typically has the effect of decreasing their porosity and stability toward thermal activation.

Elaboration of Porous Salts.

A large library of novel porous salts based on charged coordination cages was synthesized via straightforward salt metathesis reactions. For these, solutions of salts of oppositely charged coordination cages are mixed to precipitate MOF-like permanently porous products where metal identity, pore size, ligand functional groups, and surface area are highly tunable. For most of these materials, the constituent cages combine in the ratios expected based on their charge.

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.

Using Low-Pressure Methane Adsorption Isotherms for Higher-Throughput Screening of Methane Storage Materials.

A useful correlation between the low-pressure (up to 1.2 bar), low-temperature (195 K) and high-pressure (up to 65 bar), room temperature (298 K) methane storage properties of a range of porous materials is reported. Methane isotherms under these two sets of conditions show a remarkable agreement in both equilibrium adsorption and deliverable capacities for materials with pore volumes that are less than approximately 0.

Tuning the Porosity, Solubility, and Gas-Storage Properties of Cuboctahedral Coordination Cages via Amide or Ester Functionalization.

The molecular nature of porous coordination cages can endow these materials with significant advantages as compared to extended network solids. Chiefly among these is their solubility in volatile solvents, which can be leveraged in the synthesis, characterization, modification, and utilization of these adsorbents. Although cuboctahedral, paddlewheel-based coordination cages have shown some of the highest surface areas for coordination cages, they often have limited solubility.

A Charged Coordination Cage-Based Porous Salt.

Metal-organic frameworks and porous coordination cages have shown incredible promise as a result of their high tunability. However, syntheses pursuing precisely targeted mixed functionalities, such as multiple ligand types or mixed-metal compositions are often serendipitous, require postsynthetic modification strategies, or are based on complex ligand design. Herein, we present a new method for the controlled synthesis of mixed functionality metal-organic materials via the preparation of porous salts.

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

Atomistic control of the coordination environment of lattice ions and the distribution of metal sites within crystalline mixed-metal coordination polymers remain significant synthetic challenges. Herein is reported the mechanochemical synthesis of a reticular family of crystalline heterobimetallic metal-organic frameworks (MOFs) is now achieved by polymerization of molecular Ru [II,III] complexes, featuring unprotected carboxylic acid substituents, with Cu(OAc) . The resulting crystalline heterobimetallic MOFs are solid solutions of Ru and Cu sites housed within [M L ] phases.

Elucidating the Structure of the Metal-Organic Framework Ru-HKUST-1.

Ru-HKUST-1 (; ) has received considerable attention as a result of its structure type, tunability, and the redox-active nature of its constituent metal paddlewheel building units. As compared to some of the other members of the HKUST-1 family, its surface area is typically reported as ~25% lower than expected. In contrast to this, a related ruthenium-based porous coordination cage, , displays the expected surface area when compared to and analogs.

Electrochemically Mediated Syntheses of Titanium(III)-Based Metal-Organic Frameworks.

Although metal-organic frameworks featuring coordinatively unsaturated transition metal sites are relatively common, examples with redox-active cations are rare. In this report, we describe the electrochemically mediated synthesis of Ti-MIL-101 from the inexpensive Ti precursor TiCl. The framework obtained via electrosynthesis is identical to that prepared from the significantly more expensive and air-sensitive starting material TiCl.