Framework Stability and Brønsted Acidity of Isomorphously Substituted Interlayer‐Expanded Zeolite COE‐4: A Density Functional Theory Study |
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| Authors: | Haichao Li Prof Dr Danhong Zhou Dr Dongxu Tian Prof Dr Chuan Shi Dr Ulrich Müller Dr Mathias Feyen Dr Bilge Yilmaz Prof Dr Hermann Gies Prof Dr Feng‐Shou Xiao Prof Dr Dirk De Vos Prof Dr Toshiyuki Yokoi Prof Dr Takashi Tatsumi Prof Dr Xinhe Bao Prof Dr Weiping Zhang |
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| Institution: | 1. State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, (PR China);2. Institute of Chemistry for Functionalized Materials, Liaoning Normal University, Dalian 116029 (PR China);3. BASF SE, Chemicals Research and Engineering, 67056 Ludwigshafen (Germany);4. BASF Corporation, Chemicals Research and Engineering, Iselin, NJ 08830 (USA);5. Institute für Geologie, Mineralogie und Geophysik, Ruhr‐Universit?t Bochum (Germany);6. Department of Chemistry, Zhejiang University, Hangzhou 310028 (PR China);7. Centre for Surface Chemistry and Catalysis, K. U. Leuven, Leuven (Belgium);8. Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama (Japan);9. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Dalian 116023 (PR China) |
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| Abstract: | COE‐4 zeolites possess a unique two‐dimensional ten‐ring pore structure with the Si(OH)2 hydroxyl groups attached to the linker position between the ferrierite‐type layers, which has been demonstrated through the interlayer‐expansion approach in our previous work (H. Gies et al. Chem. Mater. 2012 , 24, 1536). Herein, density functional theory is used to study the framework stability and Brønsted acidity of the zeolite T‐COE‐4, in which the tetravalent Si is isomorphously substituted by a trivalent Fe, B, Ga, or Al heteroatom at the linker position. The influences of substitution energy and equilibrium geometry parameters on the stability of T‐COE‐4 are investigated in detail. The relative acid strength of the linker position is revealed by the proton affinity, charge analysis, and NH3 adsorption. It is found that the range of the 〈T‐O‐Si〉 angles is widened to maintain the stability of isomorphously substituted T‐COE‐4 zeolites. The smaller the 〈O1‐T‐O2〉 bond angle is, the more difficult is to form the regular tetrahedral unit. Thus, the substitution energies at the linker positions increase in the following sequence: Al‐COE‐4 < Ga‐COE‐4 < Fe‐COE‐4 < B‐COE‐4. The adsorption of NH3 as a probe molecule indicates that the acidity can affect the hydrogen‐bonding interaction between (N?H???O2) and (N???H?O2). The relative Brønsted‐acid strength of the interlayer‐expanded T‐COE‐4 zeolite decreases in the order of Al‐COE‐4 > Ga‐COE‐4 > Fe‐COE‐4 > B‐COE‐4. These findings may be helpful for the structural design and functional modification of interlayer‐expanded zeolites. |
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| Keywords: | Brø nsted acidity density functional calculations interlayer pore expansion isomorphously substituted COE‐4 lamellar zeolites |
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