Metal-organic frameworks (MOFs) containing undercoordinated metal centers in their framework have been suggested for adsorption and catalytic applications. The open site in the coordination sphere of the metal cation can act as a strong adsorption site for certain molecules and, hence, affords highly selective separations compared to MOFs with fully coordinate metal centers. In addition, the coordinatively unsaturated metal cations can be used as catalytic centers for various reactions. Recently, a Computationally Ready Experimental (CoRE) MOF database [1] has been compiled which includes about 5000 MOF structures. Our interest is to detect materials within this database with undercoordinated metal cations. For an efficient data mining on the CoRE database, we have developed a computational tool for the identification of open metal sites. The computational screening of MOFs is based on the characterization of the first coordination sphere of the metal centers and on their accessibility for guest molecules. A statistical analysis of the CoRE database is provided. This tool is transferable to other databases of materials. The applicability of the data mining tool is demonstrated with two examples. The first example consists of the identification of Mg-based MOFs with exposed metal sites for CO2 adsorption studies. We identified 51 MOFs with unsaturated Mg sites and assessed their affinity towards CO2 by computing binding energies using periodic DFT calculations. The second application is the identification of Fe-MOFs which can potentially stabilize the highly reactive Fe(IV)-oxo intermediate. Recently, the catalytic behavior of the Fe-diluted Mg2(dobdc) MOF has been attributed to such an intermediate [2,3]. 43 MOF structures with coordinatively unsaturated iron centers were found which are examined by means of electronic structure theory for the stability of such an intermediate. [1] Y. G. Chung, J. Camp, M. Haranczyk, B. J. Sikora, W. Bury, V. Krungleviciute, T. Yildirim, O. K. Farha, D. S. Sholl, R. Q. Snurr, Chem. Mater. Accepted. [2] D. J. Xiao, E. D. Bloch, J. A. Mason, W. L. Queen, M. R. Hudson, N. Planas, J. Borycz, A. L. Dzubak, P. Verma, K. Lee, F. Bonino, V. Crocellà, J. Yano, S. Bordiga, D. G. Truhlar, L. Gagliardi, C. M. Brown, J. R. Long, Nat. Chem. 2014, 6, 590. [3] P. Verma, K. D. Vogiatzis, N. Planas, J. Borycz, D. Xiao, J. R. Long, L. Gagliardi, D. G. Truhlar, In Preparation.

Computational screening of MOFs with open metal sites for adsorption and catalysis applications

249th National Meeting (2015)

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