Professor Tianbo Liu of Lehigh University is supported by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry for an International Collaboration in Chemistry (ICC) grant to develop rational methods for the synthesis of new type of nanoporous molecular capsules and investigate their complex interaction with counterions. Polyoxometalate clusters with specific surface functionalities of the crown-ether type and a variety of porous Keplerate nanocapsules with tunable pore sizes and charges will be synthesized. The new capsules will be used as model systems to explore their interactions with small counter-ions, counter-ion exchange and replacement, counter-ion transport over the membranes of Keplerate assemblies, and the nature of the surface water ligands on the capsules. This work includes an international collaboration with Professor Achim Müller of the University of Bielefeld (Germany). Professor Müller's work is supported by the Deutsche Forschungsgemeinschaft German Research Foundation (DFG) of Germany.
This research will provide important knowledge for the design and preparation of new materials with catalytic, electronic, and magnetic properties. The capsules synthesized may also serve as models for biological and bio-mimetic processes. This project will, therefore, impact diverse areas (including chemistry, biological science, and materials science). Furthermore, this international collaboration provides unique research environments for training students and postdoctoral researchers.
This international collaborative project (between the PI’s group at Lehigh University (now at University of Akron) and Professor Achim Müller’s group at University of Bielefeld, Germany) is aiming for understanding the complex interaction between counter-ions and giant, porous capsules in solution. The Bielefeld group is the world famous group on synthesizing such porous, soluble, moelcular metal-oxide capsules with a few nanometers in size. The Akron group is well known for studying solution properties of various complex systems, especially the behaviors of large, charged solution ions (macroions), colloids, surfactants and polymers. The joint project has gone very well since it initiated. About 17 high quality papers are published in world-leading journals, including Science, Journal of the American Chemical Society and Angewantde Chemie International Edition. Thisw can only be acheived by the close collaboration between the two groups. The two groups have been keeping extensively exchanging ideas during the grant period. The major discosveries from this grant include the detailed molelcular level stuydies on the distribution of the counterions around and inside the capsules, spontaneous and passive transport of the counterions across the capsules, the locations of coutnerions inside the capsules, etc. With mroe and more types of metal-oxide capsules are synthesized and more and more types of counterions are applied, the related phenomena are still expanding drastically. The most important discovery should be mentioned specifically here. We found that when two types of almost identical capsules stay in the same dilute aqueous solution (they might have tiny differences in charge, shape or even one central metal ion), they can strictly "recognize" their own type when they spontaneously self-assemble into large, hollow, spherical, single-layered "blackberry" structures, demonstrating the level of "intelligence" similar to complicated biological macromolecules. This unexpected discovery deserves further studies as it is directly related to some fundamental scientific questions such as the self-recognition phenomenon of biomolecules and the homochirality puzzle. This work was published in Science. The joint project also contributed greatly to the education of the next generation of scientists. Both groups have graduated several Ph.D. students and several undergraduate students who worked on this project. Particularly, a high school student from the Parkland High School (PA) who worked on this project won the Intel Science Talent Search Finalist (top 40 nationwide) and had competed in Washington DC. Now she is studying chemistry at Stanford University.
