Post-Assembly Transformations of Porphyrin-Containing Metal-Organic Framework (MOF) Films Fabricated Via Automated Layer-By-Layer Coordination

Metal–organic frameworks (MOFs) are hybrid materials composed of inorganic vertices connected to organic linkers. Due to the plethora of available linkers and vertices, MOFs can be easily tuned towards specific applications such as electrochromics¹ and catalysis². For some of these applications, it is desirable that MOFs be deposited as thin films. Among the most versatile and useful approaches to MOF film synthesis is layer-by-layer (LbL) coordination also called liquid-phase epitaxy.³ This approach successively and repetitively introduces solutions of each framework building block into contact with functionalized substrate and subsequently the growing MOF film. The advantage of LbL over other techniques is that MOF layer thicknesses can be controlled with molecular-scale precision. Thus, complex, multifunctional crystalline MOF structures are obtainable.  The presentation will demonstrate the robustness of LbL-assembled pillared-paddlewheel-type MOF films by utilizing solvent-assisted linker exchange (SALE) or post-assembly linker metalation towards the conversion of one LbL film (L2-MOF) to another LbL film (SALEF-1 and Mg-L2-MOF).⁴ Notably, Mg-L2-MOF cannot be formed through other de novo strategies. While beyond the scope of our initial investigation, we believe that the ability of the known metal lability of magnesiated porphyrins should facilitate incorporation of other metal ions, including weakly bound ions, displaying interesting redox and photophysical behaviors. The findings effectively diversify the arsenal of techniques that can be deployed to obtain desired MOF films for energy conversion applications.

References

1. Hod, I.; Bury, W.; Karlin, D. M.; Deria, P.; Kung, C. W.; Katz, M. J.; So, M. C.; Klahr, B.; Jin, D.; Chung, Y. W.; Odom, T. W.; Farha, O. K.; Hupp, J. T. Adv. Mater., 2014, 26, 6295.
2. Nguyen, H. G. T.; Schweitzer, N. M.; Chang, C., Drake, T. L.; So, M. C.; Stair, P. C.; Farha, Omar K.; Hupp, J. T., Nguyen, S. T., ACS Catal., 2014, 4, 2496.
3. So, M. C.; Jin, S.; Son, H.-J.; Farha, O. K.; Wiederrecht, G. P.; Hupp, J. T., J. Am. Chem. Soc., 2013, 135, 15698.
4. So, M. C.; Beyzavi, M. H.; Sawhney, R.; Shekah, O.; Eddaoudi, M.; Al-Juaid, S. S.; Hupp, J. T.; Farha, O. K., Chem. Commun., 2014, DOI: 10.1002/adma.201401940.