AbstractMetal-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 separtation1, catalysis2, and drug encapsulation3 among others. Organic linkers for MOF synthesis are chosen or designed based on connectivity, rigidity, and additional functionality. Porphyrin based ligands are of particular interest due to their unique photo-, electro-, and catalytic properties.4 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. Conventional porphyrin ligands for MOF synthesis contain two or four terminal carboxy groups for metal binding. However, many of these structures require an additional �pillar� molecule in order to form 3D porous structures, which inherently increases the complexity of the crystallization process.6 Thus, one recent strategy in ligand design is to maintain the high symmetry and rigidity in the organic linker, yet increase the number of carboxy binding sites, which in effect eliminates the need for an additional pillar molecule (Fig. 1).7,8Based on our custom designed octatopic porphyrin ligand, this stategy has shown a great deal of success in forming 3D MOF frameworks (Fig. 2).Figure 1.  (left) Conventional pillared-porphyrin based MOF assembly; (right) New �pillar-free� octatopic porphyrin MOF assembly. Yellow cylinders represent metal binding sites.Figure 2.  MOF structures synthesized to date based on our custom designed octatopic porphyrin ligand. Yellow cylinders represents void channels in the structure while red spheres represent void cages.References1.   Murray, L. J.; Dinca, M.; Long, J. R. Chem. Soc. Rev., 2009, 38  , 1294.2.   Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. T.; Hupp, J. T. Chem. Soc. Rev., 2009, 38  , 1450.3.   Huxford, R. C.; Rocca, J. D.; Lin, W. Curr. Opin. Chem. Biol., 2010, 14  , 262.4.   (a) Kosal, M. E.; Suslick, K. S. J. Solid State Chem., 2000, 152  , 87�98; (b)Kosal, M. E.; Chou, J. H.; Wilson S. R.; Suslick, K. S.; Nat. Mater., 2002, 1  , 118�121; (c) Suslick, K. S.; Bhyrappa, P.; Chou, J. H.; Kosal, M. E.; Nakagaki, S.; Smithenry, D. W.; Wilson, S. R. Acc. Chem. Res., 2005, 38  , 283�291; (d) Burnett, B. J.; Barron, P. M.; Hu, C.; Choe, W. J. Am. Chem. Soc., 2011, 133  , 9984�9987; (e) DeVries, L. D.; Barron, P. M.; Hurley, E. P; Hu, C.; Choe, W. J. Am. Chem. Soc., 2011, 133  , 14848�14851; (f) Lee, C. Y.; Farha, O. K.; Hong, B. J.; Sarjeant, A. A.; Nguyen, S. B. T.; Hupp, J. T. J. Am. Chem. Soc., 2011, 133  , 15858�15861.5.   (a) Shultz, A. M.; Farha, O. K.; Hupp, J. T.; T. Nguyen, S. T. J. Am. Chem. Soc., 2009, 131  , 4204�4205; (b) Farha, O. K.; Shultz, A. M.; Sarjeant, A. A.; Nguyen, S. T.; Hupp, J. T. J. Am. Chem. Soc., 2011, 133  , 5652�5655.6.   (a) Chung, H.; Barron, P. M.; Novotny, R. W.; Son, H.-T.; Hu, C.; Choe, W. Cryst. Growth Des., 2009, 9  , 3327-3332; (b) Burnett, B. J.; Barron, P. M.; Hu C.; Choe, W. J. Am. Chem. Soc., 2011, 133  , 9984-9987; (c) Choi, E.-Y.; Barron, P. M.; Novotny, R. W.; Son, H.-T.; Hu C.; Choe, W. Inorg. Chem., 2009, 48  , 426-428.7.   (a) Yang, X-L; Xie, M-H; Zou, C.; He, Y.; Chen, B.; O'Keeffe, M.; Wu, C. J. Am. Chem. Soc., 2012, 134  , 10638-10645; (b) Wang, X-S; Chrzanowski, M; Gao, W-Y; Wojtas, L; Chen, Y-S; Zaworotko, M. J.; Ma, S. Chem. Sci., 2012, 3  , 2823-2827; (c) Wang, X-S; Chrzanowski, Kim, C.; M; Gao, W-Y; Wojtas, L; Chen,Y.S.; Zhang, P. X. ; Ma, S. Chem. Commun., 2012, 48  , 7173-7175.8.   (a) Johnson, J. A.; Lin, Q.; Wu, L.-C.; Obaidi, N.;Olson,Z. L.;Reeson, T. C.; Chen Y.-S.; Zhang, J. Chem. Commun., 2013,49  , 2828-2830. (b) Johnson, J. A.; Chen, S; Reeson, T. C.; Chen Y.-S.; Zeng, X. C.; Zhang, J. Nat. Chem.  Submitted.

"Pillar Free" porphyrin MOFs based on a custom designed octatopic porphyrin linker

247th National Meeting (2014)

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