characterization of post-synthetic metalation in porous salt thin films.

Post-synthetic metalation and metathesis chemistry are central to rational synthesis of metal-organic frameworks (MOFs) that are unavailable by direct self-assembly. The inherent microcrystallinity and heterogeneous nature of many MOFs renders characterization of the rate, extent, and distribution of post-synthetic modifications challenging. Here we describe the deposition of optically transparent, permanently porous thin films comprised of peripherally carboxylated free-base porphyrins and cationic porous molecular cages.

Role of Solvent Decomposition in the Synthesis and Composition of Porous Zirconium-Based Coordination Cages.

Porous zirconium-based coordination cages are promising materials for applications in gas adsorption, catalysis, and molecular separation due to their tunability and stability. However, their synthesis is often complicated by the formation of competing phases, including insoluble or poorly soluble byproducts that impact purity and composition. Moreover, product composition and solubility can vary widely due to factors such as humidity, seasonal fluctuations, and lab-to-lab variations, highlighting the inherent lack of robustness in these syntheses.

Post-synthetic modification of amine-functionalized permanently porous coordination cages.

This manuscript explores the post-synthetic modification (PSM) of amine-functionalized porous coordination cages, specifically focusing on the formation of imine bonds through reactions with aldehydes. Targeting various cage topologies, including zirconium-, magnesium-, and molybdenum-based structures, we demonstrate the tunability of cage solubility and porosity through selective functionalization where the proximity of amine groups on the parent cage impacts the extent of modification. The work highlights the reversible nature of imine formation, offering potential applications in solubility switching and mixed-metal solid synthesis.

Tunable synthesis of heteroleptic zirconium-based porous coordination cages.

Zirconium-based porous coordination cages have been widely studied and have shown to be potentially useful for many applications as a result of their tunability and stability, likely as a result of their status as a molecular equivalent to the small 8 Å tetrahedral pores of UiO-66 (Zr(μ-O)(μ-OH)(COH)). Functional groups attached to these molecular materials endow them with a range of tunable properties. While so-called multivariate MOFs containing multiple types of functional groups on different bridging ligands within a structure are common, incorporating multiple functional moieties in permanently microporous molecular materials has proved challenging.

Selective Gas Adsorption in Permanently Microporous Coordination Cages with Exposed Metal Sites.

Porous coordination cages (PCCs), molecular analogs of metal-organic frameworks, offer modular platforms for studying the adsorption properties of small molecules, with coordinatively unsaturated metal centers playing a pivotal role in tuning these behaviors. In this work, we present the synthesis, activation, and detailed gas adsorption studies of second-row transition metal-based ML cuboctahedral cages, specifically Mo(bdc), Rh(bdc), and [Ru(bdc)]Cl. These materials represent rare examples of Mo-, Rh-, and Ru-based hybrid porous solids.

Solvent-free mechanochemistry for the preparation of mixed-ligand cuboctahedral porous coordination cages.

This study investigates post-synthetic ligand exchange in a series of copper(II) and chromium(II) cuboctahedral cages of the formula M(R-bdc) through solvent-free mechanochemistry for the preparation of mixed-ligand cages. While solvent-based ligand exchange does not proceed when the cages are insoluble or when they are dissolved in non-coordinating solvents, solvent-free mechanochemistry can be used to prepare a number of mixed-ligand cages featuring a variety of functional groups regardless of cage solubility. We further extend this strategy to intercage ligand exchange reactions where the solid-state reaction of cages proceeds in just ten minutes while corresponding solvent-based reactions require more than one week of reaction time.

Increasing the stability of calixarene-capped porous cages through coordination sphere tuning.

Chemically and thermally stable permanently porous coordination cages are appealing candidates for separations, catalysis, and as the porous component of new porous liquids. However, many of these applications have not turned to microporous cages as a result of their poor solubility and thermal or hydrolytic stability. Here we describe the design and modular synthesis of iron and cobalt cages where the carboxylate groups of the bridging ligands of well-known calixarene capped coordination cages have been replaced with more basic triazole units.

Synthesis of Long Chain Oxygenates via Aldol Condensation of Furfural and Acetone over Metal-Organic Frameworks.

Enormous efforts have been made to convert biomass to liquid fuels and products catalytically. Long molecules with a suitable structure are ideal precursors for fuels and value-added products. Here, a C21 oxygenate was synthesized for the first time in one step through aldol condensation of furfural and acetone over the amine-functionalized zirconium-based metal-organic framework (MOF), UiO-66-NH.

Unlocking Solid-State Organometallic Photochemistry with Optically Transparent, Porous Salt Thin Films.

Synthetic porous materials continue to garner attention as platforms for solid-state chemistry and as designer heterogeneous catalysts. Applications in photochemistry and photocatalysis, however, are plagued by poor light harvesting efficiency due to light scattering resulting from sample microcrystallinity and poor optical penetration that arises from inner filter effects. Here we demonstrate the layer-by-layer growth of optically transparent, photochemically active thin films of porous salts.

Adaptive Pore Opening to Form Tailored Adsorption Sites in a Cooperatively Flexible Framework Enables Record Inverse Propane/Propylene Separation.

A proposed low-energy alternative to the separation of alkanes from alkenes by energy-intensive cryogenic distillation is separation by porous adsorbents. Unfortunately, most adsorbents preferentially take up the desired, high-value major component alkene, requiring frequent regeneration. Adsorbents with inverse selectivity for the minor component alkane would enable the direct production of purified, reagent-grade alkene, greatly reducing global energy consumption.

Optimizing volumetric surface area of UiO-66 and its functionalized analogs through compression.

Metal-organic frameworks (MOFs) have garnered significant attention as gas storage materials due to their exceptional surface areas and customizable pore chemistry. For applications in the storage of small molecules for vehicular transportation, achieving high volumetric capacities is crucial. In this study, we demonstrate the compression of UiO-66 and a series of its functionalized analogs at elevated pressures, resulting in the formation of robust pellets with significantly increased volumetric surface areas.

Rapid post-synthetic modification of porous coordination cages with copper-catalyzed click chemistry.

Novel cobalt calixarene-capped and zirconium-based porous coordination cages were prepared with alkyne and azide functionality to leverage post-synthetic modification by click chemistry. While the calixarene-capped cages showed impressive stability when exposed to the most straightforward copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction conditions with copper(II) sulfate and sodium ascorbate as the reducing agent, milder reaction conditions were necessary to perform analogous CuAAC reactions on zirconium-based cages. Reaction kinetics were monitored by IR spectroscopy, confirming rapid reaction times (<3 hours).

Permanent Porosity in the Room-Temperature Magnet and Magnonic Material V(TCNE).

Materials that simultaneously exhibit permanent porosity and high-temperature magnetic order could lead to advances in fundamental physics and numerous emerging technologies. Herein, we show that the archetypal molecule-based magnet and magnonic material V(TCNE) (TCNE = tetracyanoethylene) can be desolvated to generate a room-temperature microporous magnet. The solution-phase reaction of V(CO) with TCNE yields V(TCNE)·0.

Porous Salts as Platforms for Heterogeneous Catalysis.

The preparation of a new class of reactive porous solids, prepared via straightforward salt metathesis reactions, is described here. Reaction of the dimethylammonium salt of a magnesium-based porous coordination cage with the chloride salt of [Cr Cl(Me cyclam)] affords a porous solid with concomitant removal of dimethylammonium chloride. The salt consists of the ions combined in the expected ratio based on their charge as confirmed by UV-vis and X-ray photoelectron spectroscopies, ion chromatography (IC), and inductively coupled plasma mass spectrometry (ICP-MS).

Aluminum-based metal-organic framework nanoparticles as pulmonary vaccine adjuvants.

The adoption of pulmonary vaccines to advantageously provide superior local mucosal protection against aerosolized pathogens has been faced with numerous logistical and practical challenges. One of these persistent challenges is the lack of effective vaccine adjuvants that could be well tolerated through the inhaled route of administration. Despite its widespread use as a vaccine adjuvant, aluminum salts (alum) are not well tolerated in the lung.

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.

Solvent-Induced Spin-State Change in Copper Corroles.

The electronic structure of copper corroles has been a topic of debate and revision since the advent of corrole chemistry. The ground state of these compounds is best described as an antiferromagnetically coupled Cu(II) corrole radical cation. In coordinating solvents, these molecules become paramagnetic, and this is often accompanied by a color change.

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.

Templated synthesis of zirconium(IV)-based metal-organic layers (MOLs) with accessible chelating sites.

Metal-organic layers (MOLs) are of great interest in heterogeneous catalysis, particularly materials that can accommodate extraneous metal centres. Here, we demonstrate a two-step preorganisation/delamination synthetic strategy using CuI as a template to prepare Zr-based MOLs with accessible 'syn' bis-pyrazolyl chelating sites (named ) that are poised for quantitative post-synthetic metalation with late transition metals.

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.

Facile and Rapid Room-Temperature Electrosynthesis and Controlled Surface Growth of Fe-MIL-101 and Fe-MIL-101-NH.

The electrochemical synthesis of metal-organic frameworks (MOFs) has been widely explored but has involved indirect routes, including anodic dissolution of solid metal electrodes or the use of interfacial redox chemistry to generate base equivalents and drive MOF assembly. These methods are limited in scope, as the former relies on the use of an anode consisting of the metal ion to be incorporated into the MOF, and the latter relies on the compatibility of the metal/ligand solution with the probase that is subsequently oxidized or reduced. We report the facile, direct electrochemical syntheses of four iron-based MOFs via controlled potential oxidation of dissolved metal cations.

Tuning water adsorption, stability, and phase in Fe-MIL-101 and Fe-MIL-88 analogs with amide functionalization.

Metal-organic frameworks (MOFs) of the MIL series of materials have been widely studied as a result of their high tunability and the diversity of structure types that exist for these typically M containing frameworks. We explored the use of amide-functionalized ligands in the synthesis of Fe-MIL-101 as a means to tune the water stability and water vapor adsorption in this important class of frameworks. We further show that slow leaching of Fe from NdFeB magnets can afford MIL-101 or MIL-88 under various conditions where the phase of the framework is controlled by length of the carbon chains on amide substituents.

Using Helium Pycnometry to Study the Apparent Densities of Metal-Organic Frameworks.

When investigating the gas storage capacities of metal-organic frameworks, volumetric values are often reported based on crystallographic densities. Although it is widely accepted that Langmuir and BET surface areas of a given MOF can vary depending on the exact synthetic conditions used to prepare the materials, it is rare that deviations in density from the optimal crystallographic density are considered. The actual (apparent) densities of these materials are highly variable depending on the presence of defects, impurities, or multiple phases that arise during synthesis.

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.

Structure and redox tuning of gas adsorption properties in calixarene-supported Fe(ii)-based porous cages.

We describe the synthesis of Fe(ii)-based octahedral coordination cages supported by calixarene capping ligands. The most porous of these molecular cages has an argon accessible BET surface area of 898 m g (1497 m g Langmuir). The modular synthesis of molecular cages allows for straightforward substitution of both the bridging carboxylic acid ligands and the calixarene caps to tune material properties.