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Solving a MOF Mystery

MOF mystery

Metal-organic frameworks (MOFs)/semiconducting oxide heterostructures exhibit unique properties beyond those of individual components, but their design requires an understanding of energetic and kinetic controls at MOFs–substrate interfaces.

Revealing the kinetic controls of metal-organic framework/metal oxide heterostructure

August 7, 2020
August 7, 2020
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The Science                        

Metal-organic frameworks (MOFs)/semiconducting oxide heterostructures exhibit unique properties beyond those of individual components, but their design requires an understanding of energetic and kinetic controls at MOFs–substrate interfaces. Although structure relationship has been widely applied in heterostructure design, it overlooks the interplay between organic ligands, or linkers, and substrate, which defines the kinetics and energetics in the final structure. Herein, we used zeolitic imidazolate frameworks (ZIF-8) on ZnO as a model system to evaluate this interplay via in situ monitoring and simulations.

The Impact

This is the first piece of systematic research on unraveling the physical controls of linkers on metal oxide surface step kinetics by in situ atomic force microscopy monitoring combined with ab initio molecular dynamics (AIMD)—a realistic simulation of complex systems—and density-function theory (DFT), which control the dissolution kinetics of substrate, and therefore the overgrowth kinetics of MOFs/metal oxide heterostructural materials.

Summary

This research addresses two topics that are not well understood in literature: the interplay between organic linkers and substrates during MOF crystallization, as well as the mechanisms that control heterostructure formation in solutions. It is the first piece of systematic research on unraveling the physical controls of organic linkers on metal oxide step kinetics, which controls the overgrowth rate of overlayer MOF materials by in situ monitoring combined with ab initio molecular dynamics and DFT theory. The fact that the linker 2-methyl-imidazole (2-MIM) can simultaneously act by three different mechanisms is fascinating (“dissolution-promoter,” “step-pinner,” and “terrace-binder”), and is also a unique concept given that all three are observed on a single surface—the ZnO (001) face. In contrast, only “dissolution-promoter” and “terrace-binder” are identified for the ZnO (100) face—this is a novel observation. These differences define the ZnO-face-specific growth kinetics of MOF/ZnO heterostructures. In principle, our mechanism should have a wide implication for other biological, energy, and environmental heterostructural materials formation, especially in solution conditions.

PNNL Contact

Jinhui Tao
Materials Scientist, Pacific Northwest National Laboratory

Jinhui.tao@pnnl.gov

James De Yoreo
Battelle Fellow, Pacific Northwest National Laboratory

James.DeYoreo@pnnl.gov

Jun Liu
Battelle Fellow, Pacific Northwest National Laboratory

Jun.Liu@pnnl.gov  

Funding

This research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Sciences and Engineering, Synthesis and Processing Sciences Program. XRD and SEM characterization were performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy's Office of Science Biological and Environmental Research program located at Pacific Northwest National Laboratory (PNNL). Computational resources were provided by PNNL’s Research Computing and EMSL user facility.

Research topics

J. Tao et al, “Controlling Metal-Organic Framework/ZnO heterostructure kinetics through selective ligand binding to ZnO surface steps.” Chemistry of Materials, (2020) http://doi.org/10.1021/acs.chemmater.0c02123

August 6, 2020
August 6, 2020
JULY 9, 2020
Web Feature

Building a Better Battery—Faster

Researchers at PNNL have developed a software tool that helps universities, small business, and corporate developers to design better batteries with new materials that hold more energy.
APRIL 28, 2020
News Release

A Leap in Using Silicon for Battery Anodes

Researchers at PNNL have come up with a novel way to use silicon as an energy storage ingredient, replacing the graphite in electrodes. Silicon can hold 10 times the electrical charge per gram, but it comes with problems of its own.
FEBRUARY 25, 2020
Web Feature

Forces of Attraction

Weak forces are strong enough to align semiconductor nanoparticles; new understanding may help make more useful materials

Solving an ergonomic problem to enable safeguards research

WSU engineering students demonstrate their detector lifting device.

WSU engineering students (from left background) Jacob Lazaro, Darin Malihi , Martin Gastelum, and Jared Oshiro demonstrate their detector lifting device for PNNL Physicist Mike Cantaloub (left front).

PNNL-WSU collaboration develops the future workforce

February 24, 2020
February 24, 2020
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Performing nuclear safeguards work safely and developing the next generation workforce are complementary goals of a longstanding program sponsored by the National Nuclear Security Administration’s Office of International Nuclear Safeguards. This program pairs PNNL research staff with Washington State University engineering students to provide solutions to enable nuclear safeguards research at PNNL.

In December, a team of WSU students delivered their solution to some ergonomic issues faced by PNNL physicist Mike Cantaloub and his team in a laboratory containing sensitive high-purity germanium detectors. These detectors are arranged in a tall fixture containing lead shielding to reduce the effects of naturally occurring atmospheric radiation and enable the accurate identification of radioactive isotopes in samples. Staff members using this instrument have to remove a 25-lb. plug detector, reach down to place samples, and then replace the plug detector. These activities have the potential for ergonomic injury to staff members and damage to the detectors.

WSU students Darin Malihi, Jared Oshiro, Martin Gastelum, Jacob Lazaro, Nicholas Takehara, and Saul Ramos designed and fabricated equipment that works similar to the weight training machines found in a gym—a lifting arm with a counter weight. The team also developed a solution to place the sample, a holder that is affixed to the bottom of the plug detector. Their solutions allow researchers to remove the detector quickly and efficiently and avoid reaching down to place the sample for detection.

“The solution devised by the team makes day-to-day operations in this laboratory safer and more efficient for the nuclear safeguards research team," said PNNL mechanical engineer and advisor to the WSU team, Patrick Valdez.

WSU engineering students assemble their lifting device.
WSU engineering students (from left) Jacob Lazaro, Saul Ramos, Jared Oshiro, and Nicholas Takehara assemble their lifting device and arrange the sample holders for a demonstration to PNNL research staff.