School of Chemistry and Biochemistry and ‡School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
Langmuir. 2017 Oct 3;33(39):10153-10160. doi: 10.1021/acs.langmuir.7b01987. Epub 2017 Sep 21.
The external surfaces of metal-organic framework (MOF) materials are difficult to experimentally isolate due to the high porosities of these materials. MOF surface surrogates in the form of copper benzenedicarboxylate (CuBDC) nanosheets were synthesized using a bottom-up approach, and the surface interactions of water and ethanol were investigated by temperature-programmed desorption (TPD). A method of analysis of diffusion-influenced TPD was developed to measure the desorption properties of these porous materials. This approach also allows the extraction of diffusion coefficients from TPD data. The transmission Fourier transform infrared spectra, powder X-ray diffraction patterns, and TPD data indicate that water desorbs from CuBDC nanosheets with activation energies of 44 ± 2 kJ/mol at edge sites and 58 ± 1 kJ/mol at external surface and internal and pore sites. Ethanol desorbs with activation energies of 58 ± 1 kJ/mol at internal pore sites and 66 ± 0.4 kJ/mol at external surface sites. Co-adsorption of water and ethanol was also investigated. The presence of ethanol was found to inhibit the desorption of water, resulting in a water desorption process with an activation energy of 68 ± 0.7 kJ/mol.
由于这些材料的高孔隙率，金属有机骨架（MOF）材料的外表面很难通过实验进行隔离。采用自下而上的方法合成了铜对苯二甲酸酯（CuBDC）纳米片形式的 MOF 表面替代物，并通过程序升温脱附（TPD）研究了水和乙醇的表面相互作用。开发了一种分析扩散影响 TPD 的方法来测量这些多孔材料的脱附特性。这种方法还可以从 TPD 数据中提取扩散系数。传输傅里叶变换红外光谱、粉末 X 射线衍射图案和 TPD 数据表明，水从 CuBDC 纳米片的边缘位点以 44 ± 2 kJ/mol 的活化能解吸，从外部表面和内部及孔位以 58 ± 1 kJ/mol 的活化能解吸。乙醇在内部孔位以 58 ± 1 kJ/mol 的活化能解吸，在外部表面位以 66 ± 0.4 kJ/mol 的活化能解吸。还研究了水和乙醇的共吸附。发现乙醇的存在抑制了水的解吸，导致水的解吸过程具有 68 ± 0.7 kJ/mol 的活化能。
