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The research in my group is focused on the design and synthesis of novel organic functional materials targeting a broad range of environmental, energy and biological applications, such as gas separation/storage (e.g., carbon capture), hybrid nanocomposite fabrication, light harvesting, and nanomedicine. Our efforts in developing novel materials frequently lead us to explore new synthetic tools, particularly in the area of dynamic covalent chemistry (DCC) (e.g., metathesis reactions), which enable efficient materials synthesis.

SHAPE-PERSISTENT 2-D AND 3-D MOLECULAR ARCHITECTURES

In recent years, there has been intense interest in organic shape-persistent molecular architectures, including 2D macrocycles and 3D cages, which have been playing important roles in nanomaterials and nanotechnology development. Conventionally, these rigid molecules are mainly prepared via irreversible cross-coupling reactions, which are under kinetic control and usually provide very low yields of target compounds. Our group has successfully applied thermodynamically controlled, dynamic covalent chemistry (DCC) to the synthesis of various 2-D and 3-D molecules. In our approach, provided a large energy gap between the target species and other possible products, DCC is capable of generating the desired molecular architecture in high yield from readily available simple building blocks. DCC is one of the main synthetic tools in my group, and we are developing novel dynamic covalent reactions and catalysts that would enable fast reversible covalent bond formation.

ORGANIC POROUS MATERIALS

Recently, organic porous materials have rapidly emerged as promising materials for gas storage/separation. These new materials are composed of only relatively light elements (e.g. C, H, B, N, O) that are connected by strong covalent bonds, offering great thermal and chemical stability. To date, preparation of these porous materials has generally focused on synthesizing amorphous organic polymers with non-ordered structures or densely packed polymers having crystalline structures. However, these approaches usually yield insoluble polymers, and solution-processable porous materials for certain applications (e.g., membrane fabrication for gas separation) have not yet been realized. In this project, we have explored well-defined, shape-persistent, 3-D organic molecules (prepared through highly efficient DCC) as soluble organic porous materials for gas adsorption and separation. Our group also developed "cage-to-framewok" strategy to construct novel organic porous materials using well-defined 3-D cages as building blocks. Our "cage-to-framework" strategy would enable efficient encoding of both dimensional (pore size/distribution) and functional information (guest recognition, sensing, catalysis, etc.) within the individual cage molecule into the final frameworks, enabling control over their pore size/distribution and chemical nature of the surface area.

NANOMATERIALS FOR BIOMEDICAL RESEARCH

Nanomedicine has been emerging as an active and promising research area with emphasis on exploiting the unique properties of nanomaterials for therapeutics and targeted drug delivery. In searching for nanocages that are compatible with biological systems, we discovered a subset of COPs that are fluorescent and enter mammalian cells efficiently. In this project, we aim to develop novel nanohybrid materials using 3D shape-persistent organic molecular cages that can potentially be translated clinically for non-invasive delivery of therapeutic agents, diagnostics imaging and testing the efficacy of targeted therapeutic agents in vitro and in vivo.

ARTIFICIAL PHOTOSYNTHESIS

As the energy demand continues to grow and current existing fuel sources are non-renewable, efficiently converting solar energy into electricity and chemical fuels (e.g. H2) is highly desired. Tremendous research efforts have been devoted to the development of high-efficiency solar cells and artificial photosynthetic systems. We are interested in the following two areas in solar energy research: Developing organic or organometallic dye molecules with novel structural motifs for high-efficiency dye-sensitized solar cells (DSSCs); Utilizing carbon nanotubes (CNTs) and 3-D cages as the platform for modular construction of nanohybrid light harvesting systems. In both cases, the system efficiency will be optimized by varying the structure of each component through rational molecular design. The modular approach we are using would greatly facilitate the structure-activity relationship study and can provide critical knowledge for rational design of CNT-based photoactive composite materials.

• Jin, Y.; Wang, Q.; Taynton, P.; Zhang, W. Dynamic Covalent Chemistry Approach Towards 2-D Macrocycles, 3-D Molecular Cages, and Polymers. Acc. Chem. Res. 2014, 47, 1575-1586.
• Heat or Water Driven Malleability in a Highly-Recyclable Covalent Network Polymer. Taynton, P.; Yu, K.; Shoemaker, R.; Jin, Y.; Qi, H. J.; Zhang, W. Adv. Mater. 2014, 26, 3938-3942.
• Template Synthesis of Gold Nanoparticles with an Organic Molecular Cage. McCaffrey, R.; Long, H.; Jin, Y.; Sanders, A.; Park, W.; Zhang, W. J. Am. Chem. Soc. 2014, 136, 1782-1785.
• Recent Advances in Dynamic Covalent Chemistry. Jin, Y.; Yu, C.; Denman, R. J.; Zhang, W. Chem. Soc. Rev. 2013, 42, 6634-6654.
• Solution Processable Polydiacetylenes (PDAs) through Acyclic Enediyne Metathesis Polymerization. Hu, K.; Yang, H.; Zhang, W.; Qin, Y. Chem. Sci. 2013, 4, 3649-3653.
• Imine-linked Porous Polymer Frameworks with High Small Gas (H2, CO2, CH4, C2H2) Uptake and CO2/N2 Selectivity. Zhu, Y.; Long, H.; Zhang, W. Chem. Mater. 2013, 25, 1630-1635.
• Highly Active Multidentate Alkyne Metathesis Catalysts: Ligand-activity Relationship and Their Applications in Efficient Synthesis of Porphyrin-based Aryleneethynylene Polymers. Jyothish, K.; Wang, Q.; Zhang, W. Adv. Synth. Catal. 2012, 354, 2073-2078.
• Microwave-Assisted Syntheses of Highly CO2-Selective Organic Cage Frameworks (OCFs). Jin, Y.; Voss, B. A.; McCaffrey, R.; Baggett, C. T.; Noble, R. D.; Zhang, W. Chem. Sci. 2012, 3, 874-877.
• A Highly C70-Selective Shape-Persistent Rectangular Prism Constructed Through One-Step Alkyne Metathesis. Zhang, C.-X.; Wang, Q.; Long, H.; Zhang, W. J. Am. Chem. Soc. 2011, 133, 20995-21001.
• Towards Highly Active and Robust Alkyne Metathesis Catalysts: Recent Developments in Catalyst Design. Jyothish, K.; Zhang, W. Angew. Chem. Int. Ed. 2011, 50, 8478-8480.
• Highly CO2-Selective Organic Molecular Cages: What Determines the CO2 Selectivity. Jin, Y.; Voss, B. A.; Jin, A.; Long, H.; Noble, R. D.; Zhang, W. J. Am. Chem. Soc. 2011, 133, 6650-6658.
• Introducing Podand Motif to Alkyne Metathesis Catalyst Design: A Highly Active Multidentate Mo(VI) Catalyst Resisting Alkyne Polymerization. Jyothish, K.; Zhang, W. Angew. Chem. Int. Ed. 2011, 50, 3435-3438.
• Shape-Persistent Arylenevinylene Macrocycles (AVMs) Prepared via Acyclic Diene Metathesis Macrocyclization (ADMAC). Jin, Y.; Zhang, A.; Huang, Y.; Zhang, W. Chem. Commun. 2010, 46, 8258-8260.
• A Shape-Persistent Organic Molecular Cage with High Selectivity in Adsorption of CO2 over N2. Jin, Y.; Voss, B.; Noble, R. D.; Zhang, W. Angew. Chem. Int. Ed. 2010, 49, 6348-6351.
• Modular Functionalization of Carbon Nanotubes and Fullerenes. Zhang, W.; Sprafke, J. K.; Ma, M.; Tsui, E. Y.; Sydlik, S. A; Rutledge, G. C; Swager, T. M. J. Am. Chem. Soc. 2009, 131, 8446.
• Functionalization of Single-Walled Carbon Nanotubes and Fullerenes via a Dimethyl Acetylenedicarboxylate-4-Dimethylaminopyridine Zwitterion Approach. Zhang, W.; Swager, T. M. J. Am. Chem. Soc. 2007, 129, 7714.
• Shape-Persistent Macrocycles: Structures and Synthetic Approaches from Arylene and Ethynylene Building Blocks. Zhang, W.; Moore, J. S. Angew. Chem. Int. Ed. 2006, 45, 4416.
• Reaction Pathways Leading to Arylene Ethynylene Macrocycles via Alkyne Metathesis. Zhang, W.; Moore, J. S. J. Am. Chem. Soc. 2005, 127, 11863.
• Arylene Ethynylene Macrocycles Prepared by Precipitation-Driven Alkyne Metathesis. Zhang, W.; Moore, J. S. J. Am. Chem. Soc. 2004, 126, 12796.
• Highly Active Trialkoxymolybdenum(VI) Alkylidyne Catalysts Synthesized by a Reductive Recycle Strategy. Zhang, W.; Kraft, S.; Moore, J. S. J. Am. Chem. Soc. 2004, 126, 329.