Adsorbent–Adsorbate Interactions in the Oxidation of HMF Catalyzed by Ni-Based MOFs: A DRIFT and FT-IR Insight

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• 作者：Carlo Lucarelli ; Simona Galli ; Angelo Maspero ; Alessandro Cimino ; Claudia Bandinelli ; Alice Lolli ; Juliana Velasquez Ochoa ; Angelo Vaccari ; Fabrizio Cavani ; Stefania Albonetti
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：July 21, 2016
• 年：2016
• 卷：120
• 期：28
• 页码：15310-15321
• 全文大小：700K
• 年卷期：0
• ISSN：1932-7455

文摘

The three Ni-based metal–organic frameworks (MOFs) Ni(BDP), Ni(BPEB), and Ni₃(BTP)₂ [H₂BDP = 1,4-(4-bispyrazolyl)benzene; H₂BPEB = 1,4-bis(1H-pyrazol-4-ylethynyl)benzene; H₃BTP = 1,3,5-tris(1H-pyrazol-4-yl)benzene], possessing square planar, potentially accessible metal sites, were preliminarily tested as catalysts in the base-free selective oxidation of hydroxymethylfurfural to 2,5-diformylfuran (DFF). While Ni(BDP) undergoes degradation, Ni₃(BTP)₂ is the most active of the three MOFs, yielding 27% DFF after 24 h with a selectivity close to 100% under relatively mild reaction conditions (120 °C, 30 bar O₂, water as solvent). Upon flowing a model probe, in situ DRIFT and FT-IR spectroscopy were employed to rationalize the different performances of Ni(BPEB) and Ni₃(BTP)₂ in terms of adsorbate–adsorbent interactions: Not only hydrogen bonds are at work between the hydroxyl functionality of the probe and the pore walls of the MOF, but also and more importantly, bands ascribed to Ni-OR stretching are detected, denouncing the insurgence of Ni-probe interactions. The different intensity of these bands in the two cases confirms the different accessibility of the metal centers, as suggested by crystal structure analysis and catalytic tests.