Partially fluorinated MIL-101(Cr): from a miniscule structure modification to a huge chemical environment transformation inspected by 129Xe NMR
Partially fluorinated MIL-101(Cr): from a miniscule structure modification to a huge chemical environment transformation inspected by 129Xe NMR
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DOI：
10.1039/c9ta02237f
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发表时间：
2019-07-07
影响因子：
11.9
通讯作者：
Lima, Enrique
中科院分区：
文献类型：
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作者：
Diaz-Ramirez, Mariana L.;Sanchez-Gonzalez, Eli;Lima, Enrique
首次使用 2,3,5,6-四氟-1,4-苯二甲酸 (BDC-4F) 成功实现了 MIL-101(Cr) 的部分氟官能化，得到 MIL-101(Cr)-4F(1%)。通过循环伏安法测量，官能化的结果是 MIL-101(Cr)-4F(1%) 金属中心的酸性增强。对新材料的吸附性能进行了探索，并与 MIL-101(Cr) 的吸附性能进行了比较。 H2O 吸附实验表明，由于氟原子的掺入，该材料的疏水性增强。 CO2 吸附实验显示 MIL-101(Cr)-4F(1%) 的 CO2 相互作用能 (DH) 增强。 CO2 的扩散时间常数 (D-M=r(c)(2)) 显示 MIL-101(Cr) 孔内的 CO2 迁移率高于 MIL-101(Cr)-4F(1%)，这也与 MIL-101(Cr)-4F(1%) 对 CO2 的更高选择性 (a) 有关。 MIL-101(Cr)-4F(1%) 在高压（高达 90 bar）下的 O-2 吸附等温线表明 O-2 吸收量是 MOF 材料报道的最高值之一。 H-2 吸附等温线显示，在低压下，氟官能化材料具有更高的 H-2 吸收量。这归因于 H-2 分子与氟原子的偶极相互作用，并通过 H-2 的 Delta H 计算得到证实。 Xe-129 NMR实验用于研究MIL-101(Cr)-4F(1%)的非典型孔表面电子密度，证明氟原子的极化能力对高极化Xe原子的巨大影响。最后，与 MIL-101(Cr) 相比，MIL-101(Cr)-4F(1%) 对 I-2 和 H2S 的捕获显示出相当高的值。这归因于氟化孔的高偶极性和极化性。
The partial functionalisation of MIL-101(Cr) with fluorine was successfully achieved, for the first time, with 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylate (BDC-4F) affording MIL-101(Cr)-4F(1%). As a result of the functionalisation the acidity of the metal centres for MIL-101(Cr)-4F(1%) was enhanced, which was measured by cyclic voltammetry. The resulting adsorption properties of the new material were explored and compared to those of MIL-101(Cr). H2O sorption experiments demonstrated an augmented hydrophobicity of the material due to the incorporation of fluorine atoms. CO2 adsorption experiments exhibited an augmented CO2 interaction energy (DH) for MIL-101(Cr)-4F(1%). The diffusion time constant (D-M=r(c)(2)) for CO2 showed a higher CO2 mobility inside the pores of MIL-101(Cr) than in MIL-101(Cr)-4F(1%), which was also associated with a higher selectivity (a) of MIL-101(Cr)-4F(1%) towards CO2. O-2 sorption isotherms of MIL-101(Cr)-4F(1%), at a high pressure (up to 90 bar), demonstrated O-2 uptakes among the highest values reported for a MOF material. H-2 adsorption isotherms exhibited, at low pressures, higher H-2 uptakes for the fluorine functionalised material. This was attributed to dipolar interactions of H-2 molecules with the fluorine atoms and corroborated by the calculation of Delta H for H-2. Xe-129 NMR experiments were used to investigate the atypical pore-surface electron density of MIL-101(Cr)-4F(1%), demonstrating a huge effect of the polarising power of the fluorine atoms on the highly polarisable Xe atoms. Finally, the capture of I-2 and H2S on MIL-101(Cr)-4F(1%) showed considerably higher values in comparison to MIL-101(Cr). This was attributed to the high dipolarity and polarisability of the fluorinated pores.