(217bx) Imparting New Functions to Zeolitic-Imidazolate Framework ZIF-8 Membranes Via Ligand Exchange and Post Synthetic Modification

Imparting new functions to Zeolitic-imidazolate Framework ZIF-8 Membranes via Ligand Exchange and Post Synthetic Modification

Hyuk Taek Kwon¹, and Hae-Kwon Jeong*^1,2

¹Artie McFerrin Department of Chemical Engineering and ²Materials Science and Engineering Program

Texas A&M University, College Station, TX 77843-3122

* Corresponding author: hjeong7@mail.che.tamu.edu

Metal-organic frameworks (MOFs), crystalline organic-inorganic hybrid materials, have revolutionized the research fields of porous materials since their discoveries due to their attractive features such as high surface area, regular and sub-molecular size of pore structure, and recognition and binding ability of specific molecules.¹ The diversity of MOFs, originated from theoretically unlimited combinations of organic (ligand) and inorganic (metal ion) constituents, enlarges tremendously their applications.²

Material properties of MOFs can be fine-tuned via a couple of strategies. One is through the direct construction of MOFs with pre-designed ligands and metal ions having customized functions.³ The other is post synthetic treatments, for instance, ligand/metal exchange (PSE)^4,5 and/or post synthetic modification (PSM) on organic ligands.³ The former approach has less freedom in terms of property modification because even if the synthesis starts with designed ingredients, often times it results in unintended structure or is even challenging to crystallize the MOFs due to the fact that the crystallization of MOFs is very specific to synthesis conditions such as temperature and solvent properties where ligands and synthesis solvents play a role of structure directing agent. On the other hand, the post synthetic treatments, which are performed in rather mild conditions compared to direct synthesis, can impart new functions to parent MOFs in a rather facile manner, while retaining the integrity of parent crystal structures as proven on a series of robust MOFs.^4,6

Here, we would like to present the modification of chemically inert ZIF-8 membranes, synthesized by counter diffusion concept, via ligand exchange and subsequent post synthetic modification. The effect of newly introduced functional groups on membrane properties such as hydrophobicity and gas separation performance will be systematically discussed.

References and Notes

1.         Eddaoudi M, Kim J, Rosi N, et al. Systematic Design of Pore Size and Functionality in Isoreticular MOFs and Their Application in Methane Storage. Science. January 18, 2002 2002;295(5554):469-472.

2.         Kuppler RJ, Timmons DJ, Fang Q-R, et al. Potential applications of metal-organic frameworks. Coordination Chemistry Reviews. 2009;253(23–24):3042-3066.

3.         Tanabe KK, Cohen SM. Postsynthetic modification of metal-organic frameworks-a progress report. Chemical Society Reviews. 2011;40(2):498-519.

4.         Kim M, Cahill JF, Fei H, Prather KA, Cohen SM. Postsynthetic Ligand and Cation Exchange in Robust Metal–Organic Frameworks. Journal of the American Chemical Society. 2012/10/31 2012;134(43):18082-18088.

5.         Kim M, Cahill JF, Su Y, Prather KA, Cohen SM. Postsynthetic ligand exchange as a route to functionalization of 'inert' metal-organic frameworks. Chemical Science. 2012;3(1):126-130.

6.         Fei H, Cahill JF, Prather KA, Cohen SM. Tandem Postsynthetic Metal Ion and Ligand Exchange in Zeolitic Imidazolate Frameworks. Inorganic Chemistry. 2013/04/01 2013;52(7):4011-4016.