Mitchell H. Weston

Vapor-phase metalation by atomic layer deposition in a metal-organic framework

Metal-organic frameworks (MOFs) have received attention for a myriad of potential applications including catalysis, gas storage, and gas separation. Coordinatively unsaturated metal ions often enable key functional behavior of these materials. Most commonly, MOFs have been metalated from the condensed phase (i.e., from solution). Here we introduce a new synthetic strategy capable of metallating MOFs from the gas phase: atomic layer deposition (ALD). Key to enabling metalation by ALD In MOFs (AIM) was the synthesis of NU-1000, a new, thermally stable, Zr-based MOF with spatially oriented -OH groups and large 1D mesopores and apertures.

Enhanced catalytic activity through the tuning of micropore environment and supercritical CO2 processing: Al(Porphyrin)-based porous organic polymers for the degradation of a nerve agent simulant

An Al(porphyrin) functionalized with a large axial ligand was incorporated into a porous organic polymer (POP) using a cobalt-catalyzed acetylene trimerization strategy. Removal of the axial ligand afforded a microporous POP that is catalytically active in the methanolysis of a nerve agent simulant. Supercritical CO2 processing of the POP dramatically increased the pore size and volume, allowing for significantly higher catalytic activities.

Accessing functionalized porous aromatic frameworks (PAFs) through a de novo approach

Methyl-, hydroxymethyl-, and phthalimidomethyl-functionalized versions of the porous organic polymer PAF-1 have been obtained through de novo synthesis. The CO2 adsorption capacity of PAF-1–CH2NH2, obtained through the post-synthesis deprotection of PAF-1–CH2–phthalimide, has been shown to exceed that of PAF-1.

Metal–Organic Frameworks for Oxygen Storage

We present a systematic study of metal-organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10,000 MOFs for the adsorption of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST-1 (Cu-BTC) and NU-125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST-1 and NU-125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU-125 has an increased excess capacity for oxygen of 237% and 98%, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications.

Removal of airborne toxic chemicals by porous organic polymers containing metal–catecholates

Porous organic polymers bearing metal-catecholate groups were evaluated for their ability to remove airborne ammonia, cyanogen chloride, sulphur dioxide, and octane by micro-breakthrough analysis. For ammonia, the metal-catecholate materials showed remarkable uptake under humid conditions.

A dual approach to tuning the porosity of porous organic polymers: controlling the porogen size and supercritical CO2 processing

Porous organic polymers (POPs) with tunable pore volumes and surface areas can be made from a series of SnIV(porphyrins) functionalized with labile, bulky trans-diaxial ligands. Varying the ligand size allows for the tuning of the micropore volume while supercritical CO2 processing resulted in excellent enhancements of the total pore volumes.

Phosphine Gas Adsorption in a Series of Metal-Organic Frameworks

For the first time, phosphine adsorption has been evaluated in a series of metal-organic frameworks (MOFs). Open-metal coordination sites were found to significantly enhance the ability of MOFs to adsorb highly toxic phosphine gas, with the identity of the open-metal site also modulating the amount of gas adsorbed. The MOFs studied outperform activated carbon, a commonly used material to capture phosphine.

Utilization of Metal-Organic Frameworks for the Management of Gases Used in Ion Implantation

Metal-Organic Frameworks (MOFs) are porous extended crystalline structures comprised of organic ligands and metal units. By changing the identity of the organic ligand and metal unit utilized in the MOF synthesis, the structure, surface area, pore size, and reactivity of the MOF can be modulated. This structural flexibility means that MOFs can potentially be used in a wide range of storage, separation, and catalytic applications. There is a high level of interest in the storage, delivery, capture, and purification of ultra high-purity hazardous gases used in electronics manufacturing (electronic gases). This paper will discuss the use of MOFs as an ideal platform for product and process innovation in the electronic gas sector.