(668d) Heteroepitaxial Growth of IRMOF-n (iso-reticular MOFs) and Their Thin Films

Metal-organic frameworks (MOFs) have attracted numerous research interest due to their potential applications for hydrogen storage, selective gas adsorption, catalysis, and enantioselective separation.1 With a judicious choice of organic linker groups, it is possible to fine-tune size, shape, and chemical functionality of the cavities and the internal surfaces.

Among numerous MOFs, iso-reticular MOF (IRMOF) materials have been most extensively studied due to the simplicity of their synthesis and their potential applications for gas storage. IRMOFs are a series of metal-organic frameworks developed by Yaghi and his coworkers.2 IRMOFs consist of zinc cluster nodes and benzenedicarboxylate (BDC)-based organic linkers, sharing similar crystal structure among them.

Despite a great deal of research in the synthesis and characterization of MOFs, there have been relatively few reports on the fabrication of MOF thins films and membranes. Thin films and membranes of MOFs have great potentials for applications in membrane-based gas/liquid separations, membrane reactors, chemical sensors, and nonlinear optical devices.3

Heteroepitaxial growth of one zeolite (or a zeolite-like material) on the surface of another one has been well studied and also used in the fabrication of oriented zeolite films and membranes.4 Heteroepitaxial growth of one MOF on another one have also been reported.5

In this talk, we will present the synthesis and characterization of the heteroepitaxial growth of IRMOFs (IRMOF-1, -2, and -3) for the first time and a novel strategy to prepare a series of epitaxially grown IRMOF-n thin films from IRMOF-1 (also known as MOF-5) crystal layers. The thin films are synthesized by combining the rapid seeding of IRMOF-1 seed crystals on substrates under microwaves6 and subsequent heteroepitaxial growth of the seed crystals into IRMOF-n thin films. In particular, we will discuss the fabrication of IRMOF-2 and IRMOF-3 thin films using this strategy. IRMOF-3 is of particular interest due to the presence of amine groups in the BDC linkers. These amine groups can be functionalized so that both the pore size and the surface property of the MOF can be engineered for specific separation needs.7

1 Jeffrey R. Long and Omar M. Yaghi, Chem. Soc. Rev. 38, 1213 (2009).

2 M. Eddaoudi, J. Kim, N. Rosi et al., Science 295 (5554), 469 (2002).

3 D. Zacher, O. Shekhah, C. Wöll et al., Chem. Soc. Rev. 38, 1418 (2009).

4 H. K. Jeong, J. Krohn, K. Sujaoti et al., J. Am. Chem. Soc. 124 (44), 12966 (2002).

5 S. Ferlay and M. W. Hosseini, Chem. Commun. (7), 788 (2004).

6 Y. Yoo and H. K. Jeong, Chem. Commun. (21), 2441 (2008).

7 Z. Q. Wang and S. M. Cohen, J. Am. Chem. Soc. 129 (41), 12368 (2007).