University of Nebraska-Lincoln
604D Hamilton Hall
Lincoln, NE 68588-0304
The Zhang Lab is focused on the synthesis of novel inorganic, organic, and hybrid nanoporous materials and the understanding of their fundamental chemical, electrochemical, and photocatalytic properties for novel applications in energy, environment, and sustainable chemistry.
Porphyrinic Metal-Organic Frameworks
Metal-Organic Frameworks (MOFs) are a class of hybrid materials consisting of metal-ion clusters bound by organic linkers. The high symmetry and rigid nature of the organic ligands often leads to large pores or channels within the material allowing guest molecules to freely diffuse in. Due to their highly porous nature, MOFs have attracted interest for a variety of applications including gas adsorption and separtation, catalysis, and drug encapsulation among others. Porphyrin based ligands are of particular interest due to their unique photo-, electro-, and catalytic properties. In addition, porphyrins offer a rare example of a four-fold axis of symmetry in organic ligands which is highly desirable for designing new MOF structures. Based on our custom designed octatopic porphyrin ligand, we have shown a great deal of success in forming 3D MOF frameworks with gas-capture, catalytic, and photocatalytic properties.
Porous Organic Frameworks
Porous organic frameworks (POFs) have recently emerged as a new type of microporous materials. POFs are chemically synthesized, three-dimensional network structures formed through the assembly of either planar or contorted organic monomers. POFs are highly stable due to strong, covalent carbon-carbon/carbon-nitrogen bonds. Despite their disordered structure, POFs possess permanent, high porosity and, most importantly, chemically tailorable properties: by choosing various combinations of organic monomers, one can control the pore structure, framework, and surface functionalities of POFs and tailor them for different targeted applications. We are currently focusing on the modulating of the optoelectronic properties of POFs for new applications in light harvesting, light emission, optical sensing, and catalysis.
Photoinduced Electron Transfer
Upon excitation with visible light, photocatalyst with stable, long-lived excited states has the ability of electron transfer with organic substrates. Photoinduced electron transfer events often provide access to radical ion intermediates under extremely mild conditions, with most reactions proceeding at room temperature without the need for highly reactive radical initiators. The radicals can be used in a diverse range of reactions, such as net reductive, net oxidative, and overall redox neutral reactions. Importantly, the conversion of photocatalysts to redox-active species upon irradiation with simple household fluorescent lamps or sunlight represents a remarkable low-cost and green catalytic process.
Catalysis in Confined Spaces
Unlike conventional solution-based homogeneous catalysts, MOFs and POFs provide a unique, heterogeneous catalytic platform for chemical transformations, where the reactions occur in nano-sized spaces, which often offer good chemoselectivity for chemical reactions. It is also convenient to incorporate the stereoselectivity by introducing chiral induction group in POFs. Meanwhile, the reaction can be accelerated by the enrichment of substrate and additive within the porous MOFs and POFs, which are also easy to recover and reuse. The research focus in our laboratory is to design new MOFs and POFs that are suitable for promote organic reactions and to build a fundamental understanding of the structure-activity relationship.
(1) Johnson, J. A.; Zhang X.; Reeson, T. C.; Chen, Y. S.; Zhang, J.* Facile control of the charge density and photocatalytic activity of an anionic indium porphyrin framework via in situ metalation. Journal of the American Chemical Society 2014, 136, 15881. [Link]
(2) Zhang, X.; Lu, J.; Zhang, J.* Porosity enhancement of carbazolic porous organic frameworks using dendritic building blocks for gas storage and separation. Chemistry of Materials 2014, 26, 4023. [Link]
(3) Lu, J. and Zhang, J.* Azo-linked nanoporous polymeric organic frameworks: impact of synthetic methods on selective CO2 capture. Journal of Materials Chemistry A 2014, 2, 13831. [Link]