• Ye, Jingyun
• Farha, Omar K.
• Noh, Hyunho
• Liao, Yijun
• Peters, Aaron W.
• Otake, Ken Ichi
• Li, Zhanyong
• Hupp, Joseph T.
• Liu, Jian
• Gagliardi, Laura

Abstract

<p>To modify its steric and electronic properties as a support for heterogeneous catalysts, electron-withdrawing and electron-donating ligands, hexafluoroacetylacetonate (Facac^-) and acetylacetonate (Acac^-), were introduced to the metal-organic framework (MOF), NU-1000, via a process akin to atomic layer deposition (ALD). In the absence of Facac^- or Acac^-, NU-1000-supported, AIM-installed Ni(II) sites yield a mixture of C4, C6, C8, and polymeric products in ethylene oligomerization. (AIM = ALD-like deposition in MOFs). In contrast, both Ni-Facac-AIM-NU-1000 and Ni-Acac-AIM-NU-1000 exhibit quantitative catalytic selectivity for C4 species. Experimental findings are supported by density functional theory calculations, which show increases in the activation barrier for the C-C coupling step, due mainly to rearrangement of the siting of Facac^- or Acac^- to partially ligate added nickel. The results illustrate the important role of structure-tuning support modifiers in controlling the activity of MOF-sited heterogeneous catalysts and in engendering catalytic selectivity. The results also illustrate the ease with which crystallographically well-defined modifications of the catalyst support can be introduced when the node-coordinating molecular modifier is delivered via the vapor phase.</p>

Topics

• density
• impedance spectroscopy
• nickel
• phase
• theory
• density functional theory
• activation
• atomic layer deposition