Saifutdinov Bulat R, Isaeva Vera I, Chernyshev Vladimir V, Vergun Vadim V, Kapustin Gennady I, Ivanova Yulia P, Ilyin Mikhail M, Tkachenko Olga P, Buryak Aleksey K, Kustov Leonid M
A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Building 4, 31 Leninsky Prospect, 119071 Moscow, Russia.
Department of Chemistry, M.V. Lomonosov Moscow State University, Building 3, 1 Leninskie Gory, 119991 Moscow, Russia.
Polymers (Basel). 2022 Mar 28;14(7):1373. doi: 10.3390/polym14071373.
Composite materials have been used based on coordination polymers or microporous metal-organic frameworks (MOFs) combined with mesoporous matrices for adsorption-related techniques, which enable outflanking some adverse phenomena manifested during pristine components operation and enhance the performance and selectivity of the resulting materials. In this work, for the first time, the novel HKUST-1@BPS composites synthesized by the microwave-assisted (MW) technique starting from microporous HKUST-1 (Cu(btc)) MOF and biporous silica matrix (BPS) with bimodal mesopore size distribution were comparatively studied as materials for liquid-phase adsorption techniques utilizing the high-performance liquid chromatography (HPLC) method and benzene as a model adsorbate. It was established that the studied HKUST-1@BPS composites can function as stationary phases for HPLC, unlike the pristine HKUST-1 and bare BPS materials, due to the synergetic effect of both components based on the preliminary enhanced adsorbate mass transfer throughout the silica mesopores and, subsequently, its penetrating into HKUST-1 micropores. The suggested mechanism involves the initial deactivation of open metal Cu sites in the HKUST-1 framework structure by isopropanol molecules upon adding this polar component into the mobile phase in the region of the isopropanol concentration of 0.0 to 0.2 vol.%. Thereafter, at the medium range of varying the isopropanol concentration in the eluent of 0.2 to 0.3 vol.%, there is an expansion of the previously inaccessible adsorption centers in the HKUST-1@BPS composites. Subsequently, while further increasing the isopropanol volume fraction in the eluent in the region of 0.3 to 5.0 vol.%, the observed behavior of the studied chromatographic systems is similar to the quasi-normal-phase HPLC pattern. According to the obtained thermodynamic data, benzene adsorption into HKUST-1 micropores from solutions with a vol.% of isopropanol in the range of 0.4 to 5.0 follows the unique entropy-driven mechanism previously described for the MIL-53(Al) framework. It was found that HKUST-1 loading in the composites and their preparation conditions have pronounced effects on their physicochemical properties and adsorption performance, including the adsorption mechanism.
基于配位聚合物或微孔金属有机框架（MOF）与介孔基质相结合的复合材料已被用于吸附相关技术，这使得在原始组分运行过程中出现的一些不利现象得以克服，并提高了所得材料的性能和选择性。在这项工作中，首次对通过微波辅助（MW）技术从具有双峰介孔尺寸分布的微孔HKUST-1（Cu(btc)）MOF和双孔二氧化硅基质（BPS）合成的新型HKUST-1@BPS复合材料进行了比较研究，将其作为利用高效液相色谱（HPLC）方法和苯作为模型吸附质的液相吸附技术的材料。结果表明，与原始的HKUST-1和裸露的BPS材料不同，所研究的HKUST-1@BPS复合材料可以作为HPLC的固定相，这是由于两种组分的协同作用，基于初步增强的吸附质在整个二氧化硅介孔中的传质，随后其渗透到HKUST-1微孔中。所提出的机制涉及在异丙醇浓度为0.0至0.2 vol.%的区域中将这种极性组分添加到流动相中时，HKUST-1框架结构中的开放金属Cu位点被异丙醇分子初始失活。此后，在洗脱液中异丙醇浓度变化的中等范围内，即0.2至0.3 vol.%，HKUST-1@BPS复合材料中先前无法接近的吸附中心会扩展。随后，当洗脱液中异丙醇体积分数在0.3至5.0 vol.%的区域进一步增加时，所观察到的研究色谱系统的行为类似于准正相HPLC模式。根据获得的热力学数据，从异丙醇体积分数在0.4至5.0范围内的溶液中苯吸附到HKUST-1微孔中遵循先前针对MIL-53(Al)框架描述的独特的熵驱动机制。发现复合材料中HKUST-1的负载量及其制备条件对其物理化学性质和吸附性能，包括吸附机制有显著影响。
