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McDonald, Thomas M.

Publications and source records attributed to McDonald, Thomas M..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Cooperative chemical adsorption of acid gases in functionalized metal-organic frameworks

A system and method for acid gas separations using porous frameworks of metal atoms coordinatively bound to polytopic linkers that are functionalized with basic nitrogen ligands that expose nitrogen atoms to the pore volumes forming adsorption sites. Adjacent basic nitrogen ligands on the metal-organic framework can form an ammonium from one ligand and a carbamate from the other. The formation of one ammonium carbamate pair influences the formation of ammonium carbamate on adjacent adsorption sites. Adsorption of acid gas at the adsorption sites form covalently linked aggregates of more than one ammonium carbamate ion pair. The acid gas adsorption isotherm can be tuned to match the step position with the partial pressure of acid gas in the gas mixture stream through manipulation of the metal-ligand bond strength by selection of the ligand, metal and polytopic linker materials.

Long, Jeffrey R.↗
DOE OSTI2020

Cooperative chemical adsorption of acid gases in functionalized metal-organic frameworks

A system and method for acid gas separations using porous frameworks of metal atoms coordinatively bound to polytopic linkers that are functionalized with basic nitrogen ligands that expose nitrogen atoms to the pore volumes forming adsorption sites. Adjacent basic nitrogen ligands on the metal-organic framework can form an ammonium from one ligand and a carbamate from the other. The formation of one ammonium carbamate pair influences the formation of ammonium carbamate on adjacent adsorption sites. Adsorption of acid gas at the adsorption sites form covalently linked aggregates of more than one ammonium carbamate ion pair. The acid gas adsorption isotherm can be tuned to match the step position with the partial pressure of acid gas in the gas mixture stream through manipulation of the metal-ligand bond strength by selection of the ligand, metal and polytopic linker materials.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Amine Dynamics in Diamine-Appended Mg 2 (dobpdc) Metal–Organic Frameworks

In this work, variable-temperature 15 N solid-state NMR spectroscopy is used to uncover the dynamics of three diamines appended to the metal–organic framework Mg 2 (dobpdc) (dobpdc 4– = 4,4'-dioxidobiphenyl-3,3'-dicarboxylate), an important family of CO 2 capture materials. The results imply both bound and free amine nitrogen environments exist when diamines are coordinated to the framework open Mg 2+ sites. There are rapid exchanges between two nitrogen environments for all three diamines, the rates and energetics of which are quantified by 15 N solid-state NMR data and corroborated by density functional theory calculations and molecular dynamics simulations. The activation energy for the exchange provides a measure of the metal–amine bond strength. The unexpected negative correlation between the metal–amine bond strength and CO 2 adsorption step pressure reveals that metal–amine bond strength is not the only important factor in determining the CO 2 adsorption properties of diamine-appended Mg 2 (dobpdc) metal–organic frameworks.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Alkylamine functionalized metal-organic frameworks for composite gas separations

Functionalized metal-organic framework adsorbents with ligands containing basic nitrogen groups such as alkylamines and alkyldiamines appended to the metal centers and method of isolating carbon dioxide from a stream of combined gases and carbon dioxide partial pressures below approximately 1 and 1000 mbar. The adsorption material has an isosteric heat of carbon dioxide adsorption of greater than -60 kJ/mol at zero coverage using a dual-site Langmuir model.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Polymers functionalized with bronsted acid groups

Porous aromatic framework polymers functionalized with Bronsted acid moieties are prepared by polymerization of a three-dimensional organic aryl or heteroaryl monomer and its copolymerization with a second aryl or heteroaryl monomer functionalized with one or more Bronsted acid moiety. The polymers are characterized by a stable three-dimensional structure, which, in exemplary embodiments, includes interpenetrating subunits within one or more domain of the bulk polymer structure. The polymers are of use in methods of adsorbing ammonia and amines and in devices and systems configured for this purpose.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Alkylamine functionalized metal-organic frameworks for composite gas separations

Functionalized metal-organic framework adsorbents with ligands containing basic nitrogen groups such as alkylamines and alkyldiamines appended to the metal centers and method of isolating carbon dioxide from a stream of combined gases and carbon dioxide partial pressures below approximately 1 and 1000 mbar. The adsorption material has an isosteric heat of carbon dioxide adsorption of greater than -60 kJ/mol at zero coverage using a dual-site Langmuir model.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Uncovering the Local Magnesium Environment in the Metal–Organic Framework Mg 2 (dobpdc) Using 25 Mg NMR Spectroscopy

The incorporation of N,N'-dimethylethylenediamine into an expanded MOF-74 framework has yielded a material (mmen-Mg2(dobpdc)) exhibiting “step-shaped” CO2 adsorption isotherms. The coordination of mmen at the Mg open metal center is essential for the unique cooperative adsorption mechanism elucidated for this material. Despite its importance for carbon capture, there is as yet no experimental structure determination available for the underlying metal– organic framework Mg2(dobpdc). Our 25Mg solid-state NMR data unravel the local Mg environments in several Mg2(dobpdc) samples, unambiguously confirming the formation of fivecoordinate Mg centers in the activated material and six-coordinate Mg centers in the solvent- or diamine-loaded samples, such as mmen-Mg2(dobpdc). A fraction of the Mg centers are locally disordered due to the framework deformation accompanied by the guest distributions and dynamics.

36 MATERIALS SCIENCE↗