金属有机框架(MOF)的一个显著特征是其极高的内表面积和孔隙率。有序的晶体结构形成了清晰的孔隙和通道,使得其Brunauer-Emmett-Teller(BET)比表面积可超过7000 m²/g。这一数值远超沸石或活性炭等传统多孔材料,使得巨大的内表面积易于分子接触。 adsorption.

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金属有机框架(MOF)的一个显著特征是其极高的内表面积和孔隙率。有序的晶体结构形成了清晰的孔隙和通道,使得其Brunauer-Emmett-Teller(BET)比表面积可超过7000 m²/g。这一数值远超沸石或活性炭等传统多孔材料,使得巨大的内表面积易于分子接触。 adsorption.
The high surface area in MOFs is a direct consequence of their low-density crystalline structure. Unlike amorphous materials like activated carbon, which have a wide distribution of irregular pores, MOFs possess uniform, precisely engineered cavities. The surface area is calculated from gas adsorption isotherms, typically using nitrogen or argon at cryogenic temperatures, and applying the BET theory. The formula for the BET surface area is [latex]S_{BET} = \frac{v_m N_A s}{V_M}[/latex], where [latex]v_m[/latex] is the monolayer volume of the adsorbate gas, [latex]N_A[/latex] is Avogadro’s number, [latex]s[/latex] is the adsorption cross-section of the gas molecule, and [latex]V_M[/latex] is the molar volume of the gas.
The ability to design MOFs with very long organic linkers and low-density metal nodes allows for the creation of frameworks with extremely large void fractions, sometimes exceeding 90% of the crystal volume. For example, MOF-5, one of the archetypal MOFs, has a BET surface area of around 3,000 m²/g. Later developments, such as MOF-177 and the NU series (e.g., NU-110), pushed these values to over 7,000 m²/g and even 10,000 m²/g, respectively. This immense internal ‘real estate’ is crucial for applications that rely on surface interactions, such as gas storage, where molecules are physisorbed onto the framework’s interior surfaces, and catalysis, where active sites can be distributed throughout the material’s volume.
MOF 卓越的孔隙率和表面积
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