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Regulated synthesis of Zr-metal–organic frameworks with variable hole size and its influence on the performance of novel MOF-based heterogeneous amino acid–thiourea catalysts
RSC Advances ( IF 3.9 ) Pub Date : 2022-08-03 , DOI: 10.1039/d2ra03747e Junfeng Zhu 1 , Xiaorong Meng 1 , Wen Liu 1 , Yabing Qi 1 , Siyi Jin 1 , Shanshan Huo 2
RSC Advances ( IF 3.9 ) Pub Date : 2022-08-03 , DOI: 10.1039/d2ra03747e Junfeng Zhu 1 , Xiaorong Meng 1 , Wen Liu 1 , Yabing Qi 1 , Siyi Jin 1 , Shanshan Huo 2
Affiliation
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We present an efficient and easy synthesis method for incorporating organocatalytic moieties into Zr-metal organic frameworks (Zr-MOFs). The catalytic activity and selectivity of the new chiral catalysts were improved by adjusting the aperture of the MOF cavities. The hole size of the Zr-MOF was modulated by adding acid and replacing bridge ligands during synthesis. The difunctional chiral units of amino acid–thiourea are anchored onto the Zr-MOF by a mild synthesis method from an isothiocyanate intermediate which could effectively avoid the racemization of chiral moieties in the synthesis process. By means of specific surface area measurement (BET), scanning electron microscopy (SEM) and powder X-ray Diffraction (PXRD), it was confirmed that Zr-MOFs with different pore sizes were synthesized without breaking the basic octahedral structure of the MOF. Finally, good yields (up to 83%) and ee values (up to 73%) were achieved with the new heterogeneous catalysts in 48 hours for the aldol reaction of 4-nitrobenzaldehyde with acetone. By contrast, using the catalyst support without modulating the synthesis, the yield (30%) and the ee-value (26%) were both low. Experiments have confirmed the important influence on the reaction selectivity of providing a suitable reaction environment by controlling the aperture of MOF cavities.
中文翻译：
可变孔径Zr-金属-有机骨架的调控合成及其对新型MOF基多相氨基酸-硫脲催化剂性能的影响
我们提出了一种有效且简单的合成方法，将有机催化部分纳入Zr-金属有机框架（Zr-MOF）中。通过调节MOF空腔的孔径，提高了新型手性催化剂的催化活性和选择性。 Zr-MOF 的孔尺寸通过在合成过程中添加酸和替换桥配体来调节。通过异硫氰酸酯中间体的温和合成方法，将氨基酸硫脲的双官能手性单元固定在Zr-MOF上，可以有效避免合成过程中手性部分的外消旋化。通过比表面积测量（BET）、扫描电子显微镜（SEM）和粉末X射线衍射（PXRD），证实在不破坏MOF基本八面体结构的情况下合成了不同孔径的Zr-MOF。最终，4-硝基苯甲醛与丙酮的羟醛反应在48小时内使用新型多相催化剂实现了良好的产率（高达83%）和ee值（高达73%）。相比之下，使用催化剂载体而不调节合成，产率（30%）和ee值（26%）都较低。实验证实，通过控制MOF腔的孔径提供合适的反应环境对反应选择性有重要影响。
更新日期：2022-08-03
中文翻译：
可变孔径Zr-金属-有机骨架的调控合成及其对新型MOF基多相氨基酸-硫脲催化剂性能的影响
我们提出了一种有效且简单的合成方法，将有机催化部分纳入Zr-金属有机框架（Zr-MOF）中。通过调节MOF空腔的孔径，提高了新型手性催化剂的催化活性和选择性。 Zr-MOF 的孔尺寸通过在合成过程中添加酸和替换桥配体来调节。通过异硫氰酸酯中间体的温和合成方法，将氨基酸硫脲的双官能手性单元固定在Zr-MOF上，可以有效避免合成过程中手性部分的外消旋化。通过比表面积测量（BET）、扫描电子显微镜（SEM）和粉末X射线衍射（PXRD），证实在不破坏MOF基本八面体结构的情况下合成了不同孔径的Zr-MOF。最终，4-硝基苯甲醛与丙酮的羟醛反应在48小时内使用新型多相催化剂实现了良好的产率（高达83%）和ee值（高达73%）。相比之下，使用催化剂载体而不调节合成，产率（30%）和ee值（26%）都较低。实验证实，通过控制MOF腔的孔径提供合适的反应环境对反应选择性有重要影响。
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