High-Throughput Assisted Rationalization of the Formation of Metal Organic Frameworks in the Iron(III) Aminoterephthalate Solvothermal System
ABSTRACT Through the use of high-throughput methods, solvothermal reactions of FeCl 3 and 2-aminoterephthalic acid in protic as well as aprotic reaction media were systematically studied. Thus, the fields of formation of the isoreticular structures of MIL-53, MIL-88, and MIL-101 based on Fe(III) and aminoterephthalate could be identified for the first time. The resulting 3D framework materials with amino-functionalized pores have been characterized using X-ray diffraction; IR spectroscopy; and thermogravimetric, elemental, and energy dispersive X-ray analysis. Due to the applied high-throughput method, a high density of information was obtained in a short period of time, which allows the extraction of important reaction trends and contributes to a better understanding of the role of compositional as well as process parameters in the synthesis of inorganic-organic hybrid materials. We have found that the nature of the reaction medium has the most profound impact on structure formation. Furthermore, the concentration of the starting mixture (i.e., the solvent content) and the temperature have also been identified as key parameters for the formation of the different hybrid phases.
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ABSTRACT: ZIF-8 has been rapidly developed as a potential candidate for CO2 capture due to its low density, high surface area, and robust structure. Considering the electron-donating effect of amino functional groups, amino-modification is expected to be an efficient way to improve CO2 adsorption of ZIF-8. In this work, grand canonical Monte Carlo (GCMC) simulation was performed to study the CO2 adsorption isotherm based on ZIF-8, ZIF-8-NH2, and ZIF-8-(NH2)2. ZIF-8 was synthesized and CO2 adsorption isotherms based on ZIF-8 was measured. The experimental surface area, pore volume, and CO2 adsorption isotherm were used to validate the force field. Adsorptive capacity of ZIF-8-NH2, and ZIF-8-(NH2)2 were first estimated. The GCMC simulation results indicated that the order of increasing CO2 capacity of the ZIF-8 in the lower pressure regime is: ZIF-8 < ZIF-8-NH2 < ZIF-8-(NH2)2, and in the high pressure is: ZIF-8 < ZIF-8-(NH2)2 < ZIF-8-NH2. New adsorption sites can be generated with the existence of-NH2 groups. In addition, for non-modified and amino-modified ZIF-8, it was the first time to use density functional theory (DFT) calculations to investigate their CO2 adsorption sites and CO2 binding energies. The present work indicates that appropriate amine-functionalized can directly enhanced CO2 capacity of ZIF-8.Adsorption 02/2012; 19(1). DOI:10.1007/s10450-012-9407-1 · 1.77 Impact Factor
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ABSTRACT: 2-Amino-1,4-benzenedicarboxylic acid (NH(2)-BDC) has been found to be a compatible building block for the construction of two new metal-organic frameworks (MOFs) that have structures isoreticular to reported MOFs that use 1,4-benzenedicarboxylic acid (BDC) as a building block. DMOF-1-NH(2) (DABCO MOF-1-NH(2)) is a derivative of a previously studied MOF that contains two-dimensional square grids based on NH(2)-BDC and zinc(II) paddle-wheel units; the grid layers are connected by DABCO (1,4-diazabicyclo[2.2.2]octane) molecules that coordinate in the axial positions of the paddlewheel secondary-building units (SBUs). UMCM-1-NH(2) is an NH(2)-BDC derivative of UMCM-1 (University of Michigan Crystalline Material-1), a highly porous MOF reported by Matzger et al., and consists of both NH(2)-BDC and BTB (BTB = 4,4',4''-benzene-1,3,5-triyl-tribenzoate) linkers with Zn(4)O SBUs. The structure of UMCM-1-NH(2) was confirmed by single-crystal X-ray diffraction. By using NH(2)-BDC to generate these MOFs, the pendant amino groups can serve as a chemical handle that can be manipulated via postsynthetic modification with alkyl anhydrides. Reactions of each MOF and different anhydrides have been performed to compare the extent of conversion, thermal and structural stability, and Brunauer-Emmett-Teller surface areas afforded by the resulting materials. Under comparable reaction conditions, (1)H NMR of digested samples show that UMCM-1-NH(2) has conversions comparable to that of IRMOF-3, while DMOF-1-NH(2) only shows high conversions with smaller anhydrides. Under specific reaction conditions, higher conversions were obtained with complete retention of crystallinity, as verified by single-crystal X-ray diffraction experiments. The results presented here demonstrate three important findings: (a) NH(2)-BDC can be used as a surrogate for BDC in a number of MOFs thereby providing a handle for postsynthetic modification, (b) postsynthetic modification is a general strategy to functionalizing MOFs that can be applied to a variety of MOF structures, and (c) the topology and chemical/thermal stability of a MOF can influence the type of chemical reactions and reagents that can be used for postsynthetic modification.Inorganic Chemistry 12/2008; 48(1):296-306. DOI:10.1021/ic801837t · 4.76 Impact Factor
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ABSTRACT: Metal-organic frameworks (MOFs) with non-coordinated amino groups, i.e. IRMOF-3 and amino-functionalized MIL-53, are stable solid basic catalysts in the Knoevenagel condensation of ethyl cyanoacetate and ethyl acetoacetate with benzaldehyde. IRMOF-3DEF exhibits activities that are at least as high as the most active solid basic catalysts reported, with a 100% selectivity to the condensation product. For IRMOF-3 samples the catalytic activity correlated with the accessibility of the basic sites. Diffusion limitations could be excluded for this most active catalyst. A new MOF based on the MIL-53 topology and non-coordinated amino groups has been synthesized and characterized. Although active its poor performance in the studied Knoevenagel condensations is attributed to strong adsorption and diffusion limitations in the 1-D pore structure of this framework. The performance of the IRMOF-3 catalysts demonstrates that the basicity of the aniline-like amino group is enhanced when incorporated inside the MOF structure, increasing the pKa of the basic catalyst and more active than aniline as homogeneous catalyst. The IRMOF-3 catalysts are stable under the studied reaction conditions, and could be reused without significant loss in activity. The catalytic performance of IRMOF-3 in various solvents suggests that this open, accessible and well-defined structure behaves more like homogeneous basic catalysts, in contrast to other solid basic catalysts. By means of DRIFTS, the reaction mechanism has been elucidated, showing spectroscopic evidence of benzaldimine intermediates.Journal of Catalysis 01/2009; 261(1):75-87. DOI:10.1016/j.jcat.2008.11.010 · 6.92 Impact Factor