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In this article, silicotungstic acid (STA)-loaded metal–organic framework (MOF)-derived composites (C-STA@ZrO2) were successfully synthesized by simple strategies. X-ray diffraction, Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray, N2 physisorption, UV-vis diffuse reflection spectroscopy, and X-ray photoelectron spectroscopy techniques were used to characterize the as-obtained composites. Intriguingly, C-STA@ZrO2 exhibits excellent photocatalytic performance, and rhodamine B (RhB) (40 mg·L−1) in water can be degraded to 93.9% after 120 min of irradiation. Moreover, various catalysts, catalyst dosage, and dye concentrations on RhB degradation were evaluated. Besides, the reusability of C-STA@ZrO2 was also investigated. This work may provide a new and significant guideline for exploring excellent performance of MOF-derived hybrid material for wastewater purification.

In this article, Bi2O3@Zn-MOF hybrid nanomaterials were synthesized by supporting Zn-based metal–organic framework (Zn-MOF) through the hydrothermal method. X-ray diffractometer, Fourier transform infrared, scanning electron microscopy, energy-dispersive X-ray, N2 physisorption, X-ray photoelectron spectroscopy, and UV-Vis were used to characterize the physical and chemical properties of Bi2O3@Zn-MOF nanomaterials. The photocatalytic activity of the as-prepared hybrid has been studied over the degradation of rhodamine B (RhB). A catalytic activity of 97.2% was achieved using Bi2O3@Zn-MOF nanocomposite with the loading of 0.18 g Bi2O3, after 90 min of exposure to visible light irradiation, and the high photocatalytic performance was mainly associated with the nanorod structures, larger pore size, and broaden visible light absorption region due to the synergistic effect of the constituting materials. Furthermore, the Bi2O3@Zn-MOF nanocomposite can be reused three times and the degradation rate of RhB was maintained at 77.9%. Thus, the Bi2O3@Zn-MOF nanocomposite can act as a potential photocatalyst for the photodegradation of organic dyes in environmental applications.

In this article, Bi-based metal–organic framework-supported silicotungstic acid (STA) was synthesized by a simple hydrothermal method and used as a precursor for the preparation of the Bi-based MOF-derived catalyst (STA@C-Bi-BDC). Using a combination of FTIR, XRD, SEM-EDS, N2 adsorption–desorption, TG, UV-Vis DRS, and XPS techniques, the successful immobilization of STA groups on Bi-MOF-derived C-Bi-BDC was assessed. Furthermore, the photocatalytic performance of the as-prepared catalysts was investigated in the degradation of the RhB dye process under visible light. Within 120 min of visible light exposure, the high degradation rate of RhB (92.7%) by STA@C-Bi-BDC system was achieved, which was a lot larger than the STA (39.4%), C-Bi-BDC (59.2%), and STA@Bi-BDC (74.0%) system, and cyclic experiments exhibit that the STA@C-Bi-BDC is a relatively stable photocatalyst. More importantly, the catalyst shows high applicability for the degradation of other dyes. This study reveals a comprehensive strategy for the design of efficient Bi-based MOF-derived photocatalyst for organic dye-based wastewater treatment.

In the present study, a facile solvothermal method was used for the synthesis of silicotungstic acid (HSiW) immobilized on Ce-based metal organic framework (Ce-BDC) and embedded in Zr-based metal-organic framework (UiO-66(Zr)) composite catalyst, namely, Ce-BDC@HSiW@UiO-66 for the production of biodiesel through green fatty acid esterification. The obtained hybrids were characterized by various characterization technologies, including Fourier transform infrared, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 physisorption, X-ray photoelectron spectroscopy, and temperature-programmed desorption of NH3 (NH3-TPD) analysis. The characterization analyses showed that the hybrids have been successfully synthesized. Also, the volume and pore size of UiO-66(Zr) were changed by introducing HSiW@Ce-BDC, and the resulting Ce-BDC@HSiW@UiO-66 possessed the mesoporous structure and relatively high surface area. Simultaneously, the NH3-TPD analysis of Ce-BDC@HSiW@UiO-66 reveals that the acid strength was increased in comparison with HSiW@Ce-BDC. In addition, the composite Ce-BDC@HSiW@UiO-66 demonstrated high catalytic activity, and the oleic acid esterification gave 81.5% conversion at optimum conditions of 0.2 g catalysts, 1:30 oleic acid to methanol molar ratio at 130°C for 4 h. More interestingly, after six recycling cycles, the reduction in the conversion rate was only 4.6%, indicating that Ce-BDC@HSiW@UiO-66 has excellent reusability. Our study provides an effective approach to synthesize multifunctional hybrids for green biofuel production.

MIL-125(Ti) metal–organic framework-derived nanoporous titanium dioxide–heteropoly acid (PW–TiO2) have been synthesized by a facile hydrothermal approach and subsequent calcination, and the PW–TiO2 catalysts were investigated using various characterization technologies including FTIR, XRD, SEM, TEM, N2-physisorption, and NH3-TPD. Further, we investigated the use of PW–TiO2 composites as heterogeneous acid catalysts for the catalytic esterification of oleic acid. Among all series of catalysts, the calcined PW–TiO2 at a temperature of 350°C showed excellent activity with a high conversion of 90.5% at 160°C for 4 h. More importantly, the catalyst could be simply separated via centrifugation and reused for six cycles and shows a relatively high conversion of 74.8%.

Nickel salts of Keggin-type heteropolyacid on Zr(IV)-based metal-organic frameworks (UiO-66) has been synthesized via ion-exchange followed by a facile one-pot hydrothermal method. The synthesized catalysts underwent FT-IR, N2 adsorption-desorption, powder XRD, SEM and TEM analysis. The NiHSiW/UiO-66 catalyst was used as a new and effective solid acid in the catalytic transfer free fatty acid to biodiesel with an optimum conversion of 86.7%. The excellent activity of the NiHSiW/UiO-66 nanocatalyst was closely related to its high specific surface area, nano-sized catalyst, and the synergistic effects of NiHSiW salts and UiO-66 matrix. Importantly, a relatively stable catalytic performance was achieved for 8 repeated cycles. Finally, kinetics of the esterification reaction have been assumed to be of pseudo first order.