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In this work, we have reported the synthesis of a series of heterogeneous catalysts, viz., [HMIm]3[PW12O40]@­MOF-Fe, [HMIm]3[PMo12O40]@­MOF-Fe, and [HMIm]4[SiW12O40]@­MOF-Fe, by a simple impregnation method. The catalysts were characterized by several techniques, such as FTIR, EDX, XRD, SEM, elemental mapping, and TGA. Among these materials, [HMIm]3[PW12O40]@­MOF-Fe had more acidic sites (confirmed by potentiometric titration) and high stability around 598 °C (confirmed by TGA). The catalytic prospect of the materials was examined through selective acetalization of glycerol to solketal as a fuel additive under solvent-free and room-temperature conditions. [HMIm]3[PW12O40]@­MOF-Fe exhibited the highest catalytic activity among the three catalysts in terms of glycerol conversion (100%), solketal selectivity (100%), and solketal yield (100%). A recyclability study of [HMIm]3[PW12O40]@­MOF-Fe showed that the material could be reused for up to 7 cycles with insignificant loss in its catalytic performance.

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A novel, unique, highly effective, and recyclable heterogeneous catalyst, diethyl imidazolium hexafluorophosphate ionic liquid supported metal− organic framework ([DEIm][PF 6 ]@MOF-5), has been synthesized using a simple impregnation method at ambient temperature. Characterization of the catalyst was done through various techniques such as Fourier transform infrared (FTIR), energy dispersive X-ray, X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscopy (SEM), elemental mapping, Raman spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis (TGA) analyses. The kinetic study has shown the high catalytic performance of [DEIm][PF 6 ]@MOF-5 for the reduction of 4-nitrophenol (NP) compared to other catalysts. The catalyst also exhibited efficient electrochemical activity toward 4-NP reduction. The catalyst was recyclable for more than seven cycles without any significant loss in its catalytic performance. The recycled catalyst was further studied using XRD, FTIR, SEM, and TGA analyses to investigate the structural changes that occurred during the reaction. The catalyst maintained its structural integrity even after seven cycles.

The pyrazole moiety is found as an integral structural unit in a variety of pharmacologically and agrochemically significant chemicals. The anti-inflammatory (celecoxib), anti-obesity (rimonabant), analgesic (difenamizole), antipsychotic (CDPPB), H2-receptor agonist (betazole), and antidepressant (fezolamide) activities of pyrazole-based drugs have demonstrated their pharmacological importance. Various synthetic methodologies have been devised as a result of the above-mentioned advantages of pyrazole-based compounds, including solvent-free approach, catalyst-free method, homogeneous catalysis, heterogeneous catalysis, microwave irradiation technique, ultrasonication, etc. In the area of heterogeneous catalysis, silica functionalized catalysts have garnered a lot of interest among diverse heterogeneous catalysts. The significant advancements in silica functionalized heterogeneous catalysts for the production of pyrazole-based compounds are highlighted in this review.