CAREER: Defining Intrinsic Photophysical and Photocatalytic Properties of Zeolitic Imidazolate Frameworks

Marquette University, Milwaukee WI

Investigators

Abstract

Non-Technical Description Metal organic frameworks are an emerging class of nanoporous crystalline materials consisting of metal ions or clusters coordinated to organic ligands. With support from the Solid State and Materials Chemistry program, the Principal Investigator's NSF CAREER grant Dr. Huang will focus on the fundamental design and investigation of a promising type of metal organic framework, which possesses intrinsic photoactivity, i.e. photoactive zeolitic imidazolate frameworks (ZIFs). These materials have potential applications as catalysts in photocatalytic reactions and solar energy conversion. Dr. Huang and her team aim to uncover the unknown photophysical and photochemical properties of these materials and directly correlate these properties with their catalytic functions, thus initiating a new research direction in the field of porous materials for sustainable energy. Furthermore, the proposed research will serve as a basis to raise awareness around the critical issues of global energy production and consumption, and will help train the next generation of solar energy scientists, which are key to the long-term success of this research program and the continued development of the sustainable energy field. Technical Description The role of zeolitic imidazolate frameworks (ZIFs), an emerging subclass of metal organic frameworks, in heterogeneous catalysis has largely been to act as a simple host or inert medium for dispersing the catalytic species. Inspired by the broad absorption in UV-visible-near IR region of ZIFs with paramagnetic transition metals, this research team hypothesizes that ZIFs could be used as intrinsic photocatalytic materials rather than as inert hosts. The goals of this NSF CAREER project are to fully test this hypothesis through elucidating the photophysical and structure/function relationships of ZIFs, properties essential for their photocatalytic applications. With its focus on elucidating the fundamental understanding of the molecular-level origins of light harvesting, charge separation, photocatalytic properties, and the factors that control the efficiency of these processes, the new insights from this project will be of immense value to the future development of efficient and stable ZIFs for photocatalysis and solar energy conversion. Specific objectives are: i) using the advanced time-resolved optical and X-ray transient absorption spectroscopy to reveal the optical and structural dynamics of ZIF frameworks at the molecular level; ii) systematically exploring framework dimension and chemical composition to reveal the correlation of macroscopic structure to their microscopic properties; iii) encapsulating various chromophores in the framework to enhance the light harvesting and photocatalytic properties of ZIFs; and iv) correlating these photophysical properties with the photocatalytic performance of the designed ZIFs to determine the structure-function relationship in these porous materials.