title: Copper Benzenetricarboxylate Metal-Organic Framework Nucleation Mechanisms on Metal Oxide Powders and Thin Films formed by Atomic Layer Deposition.
abstract: Chemically functional microporous metal-organic framework (MOF) crystals are attractive for filtration and gas storage applications, and recent results show that they can be immobilized on high surface area substrates, such as fiber mats. However, fundamental knowledge is still lacking regarding initial key reaction steps in thin film MOF nucleation and growth. We find that thin inorganic nucleation layers formed by atomic layer deposition (ALD) can promote solvothermal growth of copper benzenetricarboxylate MOF (Cu-BTC) on various substrate surfaces. The nature of the ALD material affects the MOF nucleation time, crystal size and morphology, and the resulting MOF surface area per unit mass. To understand MOF nucleation mechanisms, we investigate detailed Cu-BTC MOF nucleation behavior on metal oxide powders and Al2O3, ZnO, and TiO2 layers formed by ALD on polypropylene substrates. Studying both combined and sequential MOF reactant exposure conditions, we find that during solvothermal synthesis ALD metal oxides can react with the MOF metal precursor to form double hydroxy salts that can further convert to Cu-BTC MOF. The acidic organic linker can also etch or react with the surface to form MOF from an oxide metal source, which can also function as a nucleation agent for Cu-BTC in the mixed solvothermal solution. We discuss the implications of these results for better controlled thin film MOF nucleation and growth.
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Paul C
authors.initials: PC
authors.lastname: Lemaire
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Junjie
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Williams
authors.affiliation: RTI International, 3040 East Cornwallis Road, Research Triangle Park, North Carolina 27709, United States.
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Walls
authors.affiliation: RTI International, 3040 East Cornwallis Road, Research Triangle Park, North Carolina 27709, United States.
authors.forename: Sarah D
authors.initials: SD
authors.lastname: Shepherd
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.|School of Materials Science and Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Losego
authors.affiliation: Edgewood Chemical Biological Center, 5183 Blackhawk Road, Aberdeen Proving Ground, Maryland 21010, United States.
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Peterson
authors.affiliation: Department of Chemical and Biomolecular Engineering, North Carolina State University , Raleigh, North Carolina 27695, United States.|RTI International, 3040 East Cornwallis Road, Research Triangle Park, North Carolina 27709, United States.
authors.forename: Gregory N
authors.initials: GN
authors.lastname: Parsons
keywords: Cu-BTC; HKUST-1; atomic layer deposition; hydroxy double salt; metal oxide; metal−organic framework; nucleation