R. Ameloot

Microscopic Linker Distribution in Mixed-Linker Zeolitic Imidazolate Frameworks via Computational Raman Spectroscopy: Implications for Gas Separation

A.E.J. Hoffman, J. Marreiros, S.M.J. Rogge, R. Ameloot, V. Van Speybroeck

ACS Applied Nano Materials

6, 7, 5645–5652

2023

A1

Abstract

Mixed-linker zeolitic imidazolate frameworks (ZIFs) are important candidate materials for gas separation. By changing the linker content, their pore size can be tuned, offering the potential to regulate diffusion and adsorption. An important factor affecting these properties in mixed-linker ZIFs is the linker distribution, which is difficult to characterize. In this study, the microscopic linker distribution in mixed-linker ZIF-8/ZIF-90, with respectively methyl and carboxaldehyde functionalization, is elucidated via computational Raman spectroscopy. It is shown that the typical Raman band associated with the carboxaldehyde linker is shifted due to a change in hydrogen-bonding behavior. This insight allows one to explain the microscopic linker distribution in experimental mixed-linker structures.

DOI

http://dx.doi.org/10.1021/acsanm.3c00106

How Reproducible are Surface Areas Calculated from the BET Equation?

J.W.M. Osterrieth, J. Rampersad, D. Madden, N. Rampal, L. Skoric, B. Connolly, M.D. Allendorf, V. Stavila, J.L Snider, R. Ameloot, J. Marreiros, C. Ania, D. Azevedo, E. Vilarrasa-Garcia, B.F. Santos, X.-H. Bu, Z. Chang, H. Bunzen, N.R. Champness, S.L. Griffin, B. Cheng, R.-B. Lin, B. Coasne, S. Cohen, J.C. Moreton, Y.J. Colón, L. Chen, R. Clowes, F.-X. Coudert, Y. Cui, B. Hou, D.M. D'Alessandro, P.W. Doheny, M. Dincă, C. Sun, C. Doonan, M.T. Huxley, J.D. Evans, P. Falcaro, R. Ricco, O. Farha, K.B. Idrees, T. Islamoglu, P. Feng, H. Yang, R.S. Forgan, D. Bara, S. Furukawa, E. Sanchez, J. Gascon, S. Telalović, S.K. Ghosh, S. Mukherjee, M.R. Hill, M.M. Sadiq, P. Horcajada, P. Salcedo-Abraira, K. Kaneko, R. Kukobat, J. Kenvin, S. Keskin, S. Kitagawa, K.-i. Otake, R.P. Lively, S.J.A. DeWitt, P.L. Llewellyn, B.V. Lotsch, S.T. Emmerling, A.M. Pütz, C. Martí-Gastaldo, N.M. Padial, J. García-Martínez, N. Linares, D. Maspoch, J.A. Suárez del Pino, P.Z. Moghadam, R. Oktavian, R.E. Morris, P.S. Wheatley, J. Navarro, C. Petit, D. Danaci, M.J. Rosseinsky, A.P. Katsoulidis, M. Schroeder, X. Han, S. Yang, C. Serre, G. Mouchaham, D.S. Sholl, R. Thyagarajan, D. Siderius, R.Q. Snurr, R.B. Goncalves, S. Telfer, S.J. Lee, V.P. Ting, J.L. Rowlandson, T. Uemura, T. Iiyuka, M.A. van der Veen, D. Rega, V. Van Speybroeck, S.M.J. Rogge, A. Lamaire, K.S. Walton, L.W. Bingel, S. Wuttke, J. Andreo, O. Yaghi, B. Zhang, C.T. Yavuz, T.S. Nguyen, F. Zamora, C. Montoro, H. Zhou, A. Kirchon, D. Fairen-Jimenez

Advanced Materials

34, 27, 2201502

2022

A1

Abstract

Porosity and surface area analysis play a prominent role in modern materials science. At the heart of this sits the Brunauer–Emmett–Teller (BET) theory, which has been a remarkably successful contribution to the field of materials science. The BET method was developed in the 1930s for open surfaces but is now the most widely used metric for the estimation of surface areas of micro- and mesoporous materials. Despite its widespread use, the calculation of BET surface areas causes a spread in reported areas, resulting in reproducibility problems in both academia and industry. To prove this, for this analysis, 18 already-measured raw adsorption isotherms were provided to sixty-one labs, who were asked to calculate the corresponding BET areas. This round-robin exercise resulted in a wide range of values. Here, the reproducibility of BET area determination from identical isotherms is demonstrated to be a largely ignored issue, raising critical concerns over the reliability of reported BET areas. To solve this major issue, a new computational approach to accurately and systematically determine the BET area of nanoporous materials is developed. The software, called “BET surface identification” (BETSI), expands on the well-known Rouquerol criteria and makes an unambiguous BET area assignment possible.

Gold Open Access

DOI

http://dx.doi.org/10.1002/adma.202201502

Active Role of Methanol in Post-Synthetic Linker Exchange in the Metal-Organic Framework UiO-66

J. Marreiros, C. Caratelli, J. Hajek, A. Krajnc, G. Fleury, B. Bueken, D. De Vos, G. Mali, M. Roeffaers, V. Van Speybroeck, R. Ameloot

Chemistry of Materials

31 (4), 1359-1369

2019

A1

Abstract

UiO-66 is known as one of the most robust metal-organic framework materials. Nevertheless, UiO-66 has also been shown to undergo post-synthetic exchange of structural linkers with surprising ease in some sol-vents. To date the exchange mechanism has not yet been fully elucidated. Here, we show how time-resolved monitoring grants insight into the selected case of exchanging 2-aminoterephthalic acid into UiO-66 in methanol. Analysis of both the solid and liquid phase, complemented by computational insights, revealed the active role of methanol in the creation and stabilization of metastable states in which dangling linkers are similar to monocarboxylate defects that can be introduced during UiO-66 synthesis, such dangling link-ers undergo fast exchange. The presence of missing linker or missing cluster defects at the start of the ex-change process was shown to have no considerable impact on the equilibrium composition. After the ex-change process, the incoming 2-aminoterephthalate and remaining terephthalate linkers were distributed homogeneously in the framework for the typical small crystal size of UiO-66 (≈500nm).

Open Access version available at UGent repository

Green Open Access

DOI

http://dx.doi.org/10.1021/acs.chemmater.8b04734

Towards metal–organic framework based field effect chemical sensors: UiO-66-NH2 for nerve agent detection

L. Stassen, B. Bueken, H. Reinsch, J.F.M. Oudenhoven, D. Wouters, J. Hajek, V. Van Speybroeck, N. Stock, P.M. Vereecken, R. Van Schajik, D. De Vos, R. Ameloot

Chemical Science

7, 5827-5832

2016

A1

Abstract

We present a highly sensitive gas detection approach for the infamous ‘nerve agent’ group of alkyl phosphonate compounds. Signal transduction is achieved by monitoring the work function shift of metal–organic framework UiO-66-NH2 coated electrodes upon exposure to ppb-level concentrations of a target simulant. Using the Kelvin probe technique, we demonstrate the potential of electrically insulating MOFs for integration in field effect devices such as ChemFETs: a three orders of magnitude improvement over previous work function-based detection of nerve agent simulants. Moreover, the signal is fully reversible both in dry and humid conditions, down to low ppb concentrations. Comprehensive investigation of the interactions that lead towards this high sensitivity points towards a series of confined interactions between the analyte and the pore interior of UiO-66-NH₂.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1039/C6SC00987E

A Flexible Photoactive Titanium Metal-Organic Framework Based on a [Ti-3(IV)(mu(3)-O)(O)(2)(COO)(6)] Cluster

B. Bueken, F. Vermoortele, D.E.P. Vanpoucke, H. Reinsch, C. Tsou, P. Valvekens, T. De Baerdemaeker, R. Ameloot, C. Kirschhock, V. Van Speybroeck, J. Mayer, D. De Vos

Angewandte Chemie int. Ed.

127, 14118 –14123

2015

A1

Abstract

The synthesis of titanium-carboxylate metal-organic frameworks (MOFs) is hampered by the high reactivity of the commonly employed alkoxide precursors. Herein, we present an innovative approach to titanium-based MOFs by the use of titanocene dichloride to synthesize COK-69, the first breathing Ti MOF, which is built up from trans-1,4-cyclo-hexanedicarboxylate linkers and an unprecedented [Ti-3(IV)(mu(3)-O)(O)(2)(COO)(6)] cluster. The photoactive properties of COK-69 were investigated in depth by proton-coupled electron-transfer experiments, which revealed that up to one Ti-IV center per cluster can be photoreduced to Ti-III while preserving the structural integrity of the framework. The electronic structure of COK-69 was determined by molecular modeling, and a band gap of 3.77 eV was found.

DOI

http://dx.doi.org/10.1002/anie.201505512

Electronic effects of linker substitution on Lewis acid catalysis with Metal-organic frameworks

F. Vermoortele, M. Vandichel, B. Van de Voorde, R. Ameloot, M. Waroquier, V. Van Speybroeck, D. De Vos

Angewandte Chemie int. Ed.

51(20), 4887-4890

2012

A1

Abstract

Functionalized linkers can greatly increase the activity of metal–organic framework (MOF) catalysts with coordinatively unsaturated sites. A clear linear free-energy relationship (LFER) was found between Hammett σm values of the linker substituents X and the rate kX of a carbonyl-ene reaction. This is the first LFER ever observed for MOF catalysts. A 56-fold increase in rate was found when the substituent is a nitro group.