Xianhui Bu - US grants

Technical Abstract

California State University, Long Beach (CSULB) requests a Physical Property Measurement System (PPMS). The instrument will have the following technical features: a PPMS base system with a 9 Tesla longitudinal magnet and power supply, PPMS EverCoolTM recondensing system, vibrating sample magnetometer, ac susceptibility/dc magnetization measurement option, horizontal sample rotator, ac transport property measurement system, and multi-functional probe. This state-of-the-art PPMS will be used for research into a broad range of scientific challenges in nanotechnology and material sciences, including detection of triplet superconductivity in Ferromagnet/Superconductor hybrid systems; development of nanostructured molecular or covalent superlattices and crystalline porous materials; study of dissipation mechanisms in superconducting YBa2Cu3O7 coated conductors; development of novel techniques for ultra-high resolution magnetic resonance microscopy; studies of magnetic properties on new complexes containing nitric oxide and transition metals. To promote research and teaching and maximize multi-user access, the PPMS will be located at Institute for Integrated Research in Materials, Environments and Society (IIRMES) at CSULB, the core analytical facility at California State University (CSU) system.

Non-technical Abstract

PPMS is the only instrument commercially available that provides precise, interactive, and simultaneous control of the temperature (1.9 - 400 K) and magnetic field (up to t 9 T) in a wide range. Such capability enables researchers to study magnetic, electrical, superconducting, and many other physical properties of materials that are strongly temperature- and magnetic-field dependent. The research performed on the PPMS will offer new insights into the physical properties of a diverse range of natural and synthetic materials. PPMS will serve as a major instrument essential to, but currently unavailable for the successful completion of various research programs at CSULB. PPMS will also contribute greatly to outreach and education programs. As a part of IIRMES, PPMS will serve a large academic user base in an environment that actively encourages the shared use of the instruments. This will results in efficient peer exchange and collegial interaction and foster collaborative ventures in cross disciplinary research and teaching. CSU system is the largest educational establishment in the U.S. serving a student population of over 410,000 students. The requested PPMS will be the first instrument of its kind within the CSU system to enable research in variable temperature and magnetic field environments. Among many research programs benefiting from the new instrument will be programs leading to finding new functionalities in magnetic thin films, development of advanced and functional microporus materials, better understanding of coated conductors, and development of new magnetic sensing mechanisms.

TECHNICAL SUMMARY:

The proposed research aims to develop a family of crystalline boron-imidazolate based nanoporous materials with compositional and topological features that mimic porous zeolites. These materials are unique because they are capable of integrating the advantages of coordination polymers (e.g., compositional and topological diversity) and covalent organic framework materials (e.g., lightweight). The synthetic strategy involves two major steps. The first is to create a library of boron-imidazolate molecular building blocks capable of serving as tetrahedral or trigonal vertices. These various pre-synthesized molecular building units will then be assembled with metal cations or clusters into three-dimensional infinite porous frameworks. This strategy is especially suited for the creation of ultra-light porous materials using the lightest possible elements from the periodic table (e.g., Li and B) and permits the development of materials with a variety of compositional and topological features. These crystalline porous materials will be structurally characterized and their various properties, particularly porosity and gas sorption characteristics, will be characterized to determine their application potentials in energy and environmental applications such as hydrogen storage, carbon dioxide sequestration, and selection gas separation.

NON-TECHNICAL SUMMARY:

The proposed research program aims to create a family of sponge-like porous materials for energy and environmental applications. Such materials may serve as high capacity adsorbents for on-board fuel storage or waste gas sequestration and they may also selectively trap toxic and radioactive metals for environmental remediation. The award will help the PI to design curricula and a range of research activities in solid state and materials chemistry that will provide training opportunities for undergraduate and graduate students, leading to publications and scholarly presentations involving these students. Because a large fraction of students in the PI's university and laboratory are from underrepresented groups, the program will broaden the participation of these students and promote diversity in solid state and materials research.

TECHNICAL SUMMARY:
The proposed research, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, aims to develop new synthetic methods for the creation of crystalline homochiral porous materials for enantioselective applications. While significant progress has been made in the synthesis of such materials by incorporating chiral structural building blocks, their synthesis from nonchiral building blocks remains challenging, and yet highly important. The proposed chirality induction method seeks to construct homochiral porous materials from diverse nonchiral building units while controlling absolute chirality by using inexpensive and often naturally occurring enantiopure chiral induction agents (CIA). The project will also study the metal-CIA interactions to uncover new mechanisms that can be utilized for the chirality and enantiopurity control. A range of low-cost organic and biomolecular CIAs will be studied under various synthetic conditions for their effects during crystallization of porous frameworks. New homochiral porous materials will be characterized by studying their crystal structures, porosity and surface area, thermal and chemical stability, and enantioselectivity.

NON-TECHNICAL SUMMARY:
The proposed activity, conducted at a Primarily Undergraduate Institution, seeks to introduce new synthetic concepts and methods that can be employed to create homochiral porous materials as catalysts and adsorbents for the preparation of highly useful chemicals and pharmaceuticals. The proposed research integrates a variety of research activities ranging from chemical synthesis, self-assembly and crystal growth, to crystal structure analysis and property characterizations. It will lead to the creation of new functional materials with potential technological applications and a much-enhanced understanding of synthetic and structural chemistry of solid-state materials. The PI seeks to promote teaching and training of students by establishing a highly interesting and important research program and by developing the state-of-the-art synthetic and instrumental capability to broaden learning opportunities and participation of both undergraduate and graduate students with diverse cultural backgrounds.

NON-TECHNICAL Abstract:
This project seeks to develop new synthetic concepts and methods to invent crystalline porous materials impregnated with mobile anions. The uniform and tunable pore size, together with the control over the charge and functionality of the framework combine to enable new and more efficient applications in anion exchange, separation, detection, and conduction. Nature abhors cationic frameworks and comes out with various neutralization ways to prevent their formation. This project combats this nature's tendency using novel concepts and strategies to counter such natural tendency proactively and preemptively. Being at an undergraduate institution with a large population of students including those from underrepresented groups, the PI strives to utilize the NSF support to promote teaching and training of students by establishing a highly stimulating and important research project and by developing the state-of-the-art synthetic and instrumental capability to broaden learning opportunities for students with diverse backgrounds.


TECHNICAL Abstract:
The project seeks to develop new synthetic concepts and methods to create porous materials with the positively charged framework integrating uniform and tunable pore size with mobile anions for applications such as anion exchange, sequestration, separation, sensing, as well as fast anion conduction. It deals with fundamental issues in materials design such as the control of ratio between negative and neutral functional groups and the ratio between metal ions in mix-valence or heterometallic systems. Such issues are fundamental to the control of the framework charge property and their applications. The core strategy involves designing cluster-type structural building blocks with propensity for being cationic and simultaneously inventing advanced methods to proactively prevent possible neutralization of such units. Various methods are used to tune the pore size and properties to enhance process selectivity based on size, shape, and charge of molecules and ions. The project integrates a variety of student-training activities ranging from chemical synthesis, crystal growth, to crystal structure analysis and property characterizations with the goal to broaden the participation of undergraduate and graduate students in chemical research and to promote a diverse student population in materials sciences.

This award to California State University-Long Beach is supported by the Major Research Instrumentation and the Chemistry Research Instrumentation programs to support and improve research by professor Xianhui Bu from and colleagues Michael Schramm, Young-Seok Shon and Fangyuan Tian. The institution is acquiring a single crystal X-ray difffractometer (SCXRD). In general, an X-ray diffractometer allows accurate and precise measurements of the full three-dimensional structure of a molecule, including bond distances and angles, and provides accurate information about the spatial arrangement of a molecule relative to neighboring molecules. The studies described here impact many areas, including organic and inorganic chemistry, materials chemistry, geology and biochemistry. This instrument is an integral part of teaching as well as research and research training of undergraduate students in chemistry and biochemistry at this Hispanic Serving Institution as well as California State University Los Angeles. The instrumentation provides direct research experience for students in a variety of courses distributed in various departments and other neighboring universities.

The award of the X-ray diffractometer is aimed at enhancing research and education at all levels. The science enabled by this instrument provides relevant societal benefits through the development of new materials to address energy production, new catalysts to improve the synthesis of commodity and industrial chemicals. The instrumentation is also used for studying amino-acid-based homochiral porous materials with zeolite-type frameworks and for developing acid-base stable metal-organic framework materials (MOFs). In addition, it benefits the exploration of mono and bisgold resorcinarenes as supramolecular catalysts and for investigating mechanisms of MOF catalysis based on structures of MOFs and trapped reaction intermediates (in collaboration with California State University Los Angeles). The diffractometer is also used to characterize fluorescent metal-organic frameworks for sensing explosive compounds. Additionally, the diffractometer is utilized for the structural characterization of non-heme iron nitrosyl complexes and catalysis made from monometallic palladium, platinum and iridium nanoclusters.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

NON-TECHNICAL SUMMARY

Metal-organic frameworks are molecular-scale sieves composed of metal centers coordinated to organic ligands, which results in three-dimensional structures with uniform pore size. They can enable or improve large-scale energy, health, and defense applications such as gas storage and separation, water and other chemical decontamination, direct water harvesting and carbon dioxide capture from air, and nuclear waste treatment. However, currently few metal-organic framework materials have a suitable combination of porosity and chemical stability to meet the demands of these applications. Developing chemically stable and pore-size-tunable metal-organic frameworks is among the most important scientific challenges and is the objective of this project, which is supported by the Solid State and Materials Chemistry program in the Division of Materials Research. The project aims to impart high chemical stability by simultaneously creating highly connected structural building blocks and rigid frameworks that are not easily broken down by common molecules and molecular fragments, such as water and hydroxide ions. The pore geometry of these new materials can be tuned using different combinations structural building blocks and organic ligands. By developing these new synthesis pathways new materials with the highest chemical stability among metal-organic framework materials are created that can be used under harsh chemical conditions commonly encountered in real-world applications. In addition, this project enables a variety of research activities and provides rich training opportunities for a diverse population of undergraduate and graduate students at California State University – Long Beach.


TECHNICAL SUMMARY

With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Prof. Xianhui Bu and his research group develop synthetic pathways to create a family of new ultrastable and ultratunable metal-organic framework materials. The structural platform has an extraordinary flexibility in metal-ligand bond type (e.g., metal-carboxylate, metal-azolate, metal-pyridyl), which allows a high level of control over porosity, functionality, and stability within the same isoreticular series of materials. To expand the boundaries in acid-base stability of metal-organic frameworks, the researchers synthesize chromium-trimer-based frameworks with the high-connected (higher than 6) trimer building block. Only low-connected chromium metal-organic frameworks (6 or less) were known prior to this project, and the creation of high-connected framework materials in this project with mixed Cr-O and Cr-N crosslinks further increases the kinetic inertness of trivalent metal ions and also shields the metal nodes from chemical attacks by coordinating species. The researchers also systematically explore key experimental parameters such as reaction temperature, solvent type, and modulators, all of which play a far greater role for nonlabile metal ions in this project, compared to labile ions in most metal-organic frameworks. The integrated compositional and structural features to be achieved in this project increase acid-base stability simultaneously in both low- and high-pH directions. The exceptional chemical stability of these materials can enable a broad range of applications, especially those that operate under harsh chemical conditions such as nuclear waste treatment. In addition, this project enables a variety of research activities and provides rich training opportunities for a diverse population of undergraduate and graduate students at California State University – Long Beach.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.