Characterization of Dispersed Heteropoly Acid on Mesoporous Zeolite Using Solid-State 31P NMR Spin−Lattice Relaxation

Recent Progress on Functionalized Nanoporous Heteropoly Acids: From Synthesis to Applications

Functionalized nanoporous heteropoly acids (HPAs) have garnered significant attention in recent years due to their enhanced surface area and porosity, as well as their potential for low-cost regeneration compared to bulk materials. This review aims to provide an overview of the recent advancements in the synthesis and applications of functionalized HPAs. We begin by introducing the fundamental properties of HPAs and their unique structure, followed by a comprehensive overview of the various approaches employed for the synthesis of functionalized HPAs, including salts, anchoring onto supports, and implementing mesoporous silica sieves. The potential applications of functionalized HPAs in various fields are also discussed, highlighting their boosted performance in a wide range of applications. Finally, we address the current challenges and present future prospects in the development of functionalized HPAs, particularly in the context of mesoporous HPAs. This review aims to provide a comprehensive summary of the recent progress in the field, highlighting the significant advancements made in the synthesis and applications of functionalized HPAs.

Microwave-assisted liquefaction of carbohydrates for 5-hydroxymethylfurfural using tungstophosphoric acid encapsulated dendritic fibrous mesoporous silica as a catalyst

Tungstophosphoric acid (TPA) encapsulated dendritic fibrous silica KCC-1 was prepared via a microemulsion system with the simple reflux method using cetyltrimethylammonium bromide as a structure-directing agent. The TPA impregnated on KCC-1 (ITPA-KCC-1) was also prepared for comparative. Various physicochemical techniques were used to characterize the synthesized materials and their activity evaluated in the 5-hydroxymethylfurfural (HMF) formation from carbohydrates derivatives of fructose, glucose and cellulose. The effect of various factors such as catalyst to substrate ratio, different solvents and temperature were investigated on the formation of HMF. The resultant encapsulated catalyst was very active in fructose dehydration with the yield of 92% HMF and full conversion of fructose at 120 °C for 30 min under the microwave heating condition without any salt additive in the THF solvent system as well as 95% in MIBK solvent. The HMF yield was achieved by 58% and 16.2% from glucose and cellulose in the DMSO solvent, respectively. The TPA-KCC-1 can be separated easily after reaction from the reaction mixture and reused atleast five times without substantial loss in catalytic activity. This study provides an easy encapsulation method for TPA in dendritic fibrous silica KCC-1 as a heterogeneous catalyst, and it should have great application potential in other biomass valorization processes.

Study on heteropolyacid-based catalysts with high activity and reusability for isoprene synthesis from formaldehyde and isobutene

SiW/S-1 catalysts exhibited excellent catalytic activity and reusability due to the highly dispersed SiW and MFI structure of S-1.

Synthesis of Ni(ii)-phosphotungstic acid/nanocrystalline HZSM-5 catalyst for ultra clean gasoline in a single-stage reactor

An excellent catalyst for hydrodesulfurization, aromatization and olefin hydrogenation of FCC gasoline, is designed in this paper.

A silicotungstate-based copper–viologen hybrid photocatalytic compound for efficient degradation of organic dyes under visible light

An efficient visible light responsive compound [Cu(PBPY)]₂[SiW₁₂O₄₀] (1) has been constructed by integrating a silicotungstate cluster into the copper–viologen framework. It shows high photocatalytic efficiency for the degradation of dye pollutants.

From 3D to 2D zeolite catalytic materials

Research activities and recent developments in the area of three-dimensional zeolites and their two-dimensional analogues are reviewed. Zeolites are the most important industrial heterogeneous catalysts with numerous applications. However, they suffer from limited pore sizes not allowing penetration of sterically demanding molecules to their channel systems and to active sites. We briefly highlight here the synthesis, properties and catalytic potential of three-dimensional zeolites followed by a discussion of hierarchical zeolites combining micro- and mesoporosity. The final part is devoted to two-dimensional analogues developed recently. Novel bottom-up and top-down synthetic approaches for two-dimensional zeolites, their properties, and catalytic performances are thoroughly discussed in this review.

Polyoxometalate Cluster Sensitized with Copper-Viologen Framework for Efficient Degradation of Organic Dye in Ultraviolet, Visible, and Near-Infrared Light

An efficient photocatalyst based on the broadband solar response molecular system was designed and constructed for pollutant degradation in near-neutral conditions via utilizing guest polyoxometalate cluster sensitized with electron deficient host network. Photoelectrochemical analysis reveals electron-hole pairs are generated efficiently upon both visible and NIR light excitation. Its photocatalytic activity in the visible and NIR light regions is enhanced because of the contribution from the broad absorption of copper-viologen framework and the strong host-guest interactions. This stable heterogeneous catalyst is easily recollected and regenerated without the loss of activity for the next cycle.

12-Molybdophosphoric acid anchored on aminopropylsilanized magnetic graphene oxide nanosheets (Fe3O4/GrOSi(CH2)3–NH2/H3PMo12O40): a novel magnetically recoverable solid catalyst for H2O2-mediated oxidation of benzylic alcohols under solvent-free conditions

In this work, 12-molybdophosphoric acid (H₃PMo₁₂O₄₀, HPMo) was chemically anchored onto the surface of aminosilanized magnetic graphene oxide (Fe₃O₄/GrOSi(CH₂)₃–NH₂) and was characterized using different physicochemical techniques, such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, energy-dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), BET specific surface area analysis and magnetic measurements. The results demonstrated the successful loading of HPMo (∼31.5 wt%) on the surface of magnetic aminosilanized graphene oxide. XRD patterns, N₂ adsorption–desorption isotherms and SEM images confirm the mesostructure of the sample. FT-IR and EDX spectra indicate the presence of the PMo₁₂O₄₀³⁻ polyanions in the nanocomposite. The as-prepared Fe₃O₄/GrOSi(CH₂)₃–NH₂/HPMo nanocomposite has a specific surface area of 76.36 m² g⁻¹ that is much higher than that of pure HPMo. The selective oxidation of benzyl alcohol to benzaldehyde was initially studied as a benchmark reaction to evaluate the catalytic performance of the Fe₃O₄/GrOSi(CH₂)₃–NH₂/HPMo catalyst. Then, the oxidation of a variety of substituted primary and secondary activated benzylic alcohols was evaluated with H₂O₂ under solvent-free conditions. Under the optimized conditions, all alcohols were converted into the corresponding aldehydes and ketones with very high selectivity (≥99%) in moderate to excellent yields (60–96%). The high catalytic performance of the nanocomposite was ascribed to its higher specific surface area and more efficient electron transfer, probably due to the presence of GrO nanosheets. The nanocomposite catalyst is readily recovered from the reaction mixture by a usual magnet and reused at least four times without any observable change in structure and catalytic activity.

12-Molybdophosphoric acid was anchored on magnetic aminopropylsilanized graphene oxide nanosheets and used as a magnetically recoverable catalyst for solvent-free selective oxidation of benzylic alcohols into the carbonyl compounds with H₂O₂.

Molecular and electron-spin structures of a ring-shaped mixed-valence polyoxovanadate (IV, V) studied by (11)B and (23)Na solid-state NMR spectroscopy and DFT calculations

(11)B and (23)Na solid-state nuclear magnetic resonance (NMR) spectra of ring-shaped paramagnetic crystals of H15[V7(IV)V5(V)B32O84Na4]·13H2O containing seven d(1) electrons from V(IV) were studied. Magic-angle-spinning (MAS) and multiple-quantum MAS NMR experiments were performed at moderate (9.4T) and ultrahigh magnetic fields (21.6T). The NMR parameters for quadrupole and isotropic chemical shift interactions were estimated by simulation of the NMR spectra and from relativistic density functional theory (DFT) calculations. Four Na ions incorporated into the framework were found to occupy four distinct sites with different populations. The DFT calculation showed that d(1) electrons with effectively one up-spin caused by strong antiferromagnetic interactions were delocalized over the 12V ions.

Heteropolytungstic acids incorporated in an ordered mesoporous zirconia framework as efficient oxidation catalysts

Ordered mesoporous composite materials consisting of nanocrystalline ZrO₂ and 12-phosphotungstic and 12-silicotungstic acids were synthesized and shown to be superior catalysts than individual components.