No abstract

The HKUST-1@SBA-15 composites with hierarchical pore structure were constructed by in situ self-assembly of metal-organic framework (MOF) with mesoporous silica. The structure directing role of SBA-15 had an obvious impact on the growth of MOF crystals, which in turn affected the morphologies and structural properties of the composites. The pristine HKUST-1 and the composites with different content of SBA-15 were characterized by XRD, N adsorption-desorption, SEM, TEM, FT-IR, TG, XPS, and CO-TPD techniques. It was found that the composites were assembled by oriented growth of MOF nanocrystals on the surfaces of SBA-15 matrix. The interactions between surface silanol groups and metal centers induced structural changes and resulted in the increases in surface areas as well as micropore volumes of hybrid materials. Besides, the additional constraints from SBA-15 also restrained the expansion of HKUST-1, contributing to their smaller crystal sizes in the composites. The adsorption isotherms of CO on the materials were measured and applied to calculate the isosteric heats of adsorption. The HS-1 composite exhibited an increase of 15.9% in CO uptake capacity compared with that of HKUST-1. Moreover, its higher isosteric heats of CO adsorption indicated the stronger interactions between the surfaces and CO molecules. The adsorption rate of the composite was also improved due to the introduction of mesopores. Ten cycles of CO adsorption-desorption experiments implied that the HS-1 had excellent reversibility of CO adsorption. This study was intended to provide the possibility of assembling new composites with tailored properties based on MOF and mesoporous silica to satisfy the requirements of various applications.

A new strategy was proposed to construct the ionic liquid, polyoxometalate (POM), and metal–organic framework (MOF) composite. The POM‐based MOF was synthesized by using the direct hydrothermal method. The sulfonic acid group‐functionalized ionic liquid was used for further modification of the hybrid material to realize the encapsulation of the heteropolyanion‐based ionic liquid within the cages of the MOF. The catalysts were characterized by using XRD, N2 adsorption–desorption, FTIR, SEM, TEM, elemental analysis, and TGA. The results indicated that the heteropolyanion‐based ionic liquid had been successfully encapsulated within the cages and the structure of MIL‐100 (MIL=Materials of Institut Lavoisier) remained intact. The POM–ionic‐liquid‐functionalized MOF, with high content of the active component, had both Lewis and Brønsted acid sites, which led to high catalytic activity for the esterification of oleic acid with ethanol. The esterification reaction conditions were optimized by using response surface methodology (RSM), and the corresponding conversion of oleic acid reached 94.6 %. The catalyst could be easily recovered and reused six times without significant loss of activity.