Mohammadreza Shokouhimehr

Magnetically recyclable hollow nanocomposite catalysts for heterogeneous reduction of nitroarenes and Suzuki reactions

Highly active magnetically recyclable hollow nanocomposite catalysts with a permeable carbon surface have been prepared by a simple, economical and scalable process. The designed nanocomposite exhibited excellent catalytic activities in the selective reduction of nitroarenes and Suzuki cross-coupling reactions. The catalysts could be easily separated by a magnet, and recycled consecutively.

Magnetically recyclable core–shell nanocatalysts for efficient heterogeneous oxidation of alcohols

We describe the designed fabrication of magnetically recyclable core–shell Pd nanocatalysts for the efficient oxidation of alcohols under base-free reaction conditions in water. The Pd NPs that are half-partitioned in the polymer matrix can provide not only high catalytic activity but also stabilization of the nanocatalysts under harsh reaction conditions. Furthermore the magnetic separation provides a convenient method for removing and recycling the active Pd nanocatalysts from the reaction mixture. The designed nanocatalysts can be readily synthesized in a large scale and were able to be reused for five consecutive cycles of the oxidation of cycloheptanol. The nanocatalysts present high catalytic activity in other types of catalytic reactions involving Pd NPs such as Suzuki cross-coupling and reduction of nitroarenes.

A general strategy for site-directed enzyme immobilization by using NiO nanoparticle decorated mesoporous silica.

Mesoporous materials have recently gained much attention owing to their large surface area, narrow pore size distribution, and superior pore structure. These materials have been demonstrated as excellent solid supports for immobilization of a variety of proteins and enzymes for their potential applications as biocatalysts in the chemical and pharmaceutical industries. However, the lack of efficient and reproducible methods for immobilization has limited the activity and recyclability of these biocatalysts. Furthermore, the biocatalysts are usually not robust owing to their rapid denaturation in bulk solvents. To solve these problems, we designed a novel hybrid material system, mesoporous silica immobilized with NiO nanoparticles (SBA-NiO), wherein enzyme immobilization is directed to specific sites on the pore surface of the material. This yielded the biocatalytic species with higher activity than free enzyme in solution. These biocatalytic species are recyclable with minimal loss of activity after several cycles, demonstrating an advantage over free enzymes.

One-pot synthesis of magnetically recyclable mesoporous silica supported acid–base catalysts for tandem reactions

We report one-pot synthesis of magnetically recyclable mesoporous silica catalysts for tandem acid-base reactions. The catalysts could be easily recovered from the reaction mixture using a magnet, and the pore size of the catalysts could be controlled by introducing a swelling agent, resulting in the significant enhancement of the reaction rate.

Synthesis of mesoporous tungsten oxide by template-assisted sol–gel method and its photocatalytic degradation activity

In this study, mesoporous tungsten oxide nanostructure was successfully synthesized using inexpensive peroxotungstic acid as a tungsten precursor, and pluronic P123 blockcopolymer as a template. Various techniques such as differential thermal analysis, thermogravimetric analysis, Fourier transformed infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, nitrogen adsorption/desorption analysis, and UV–Vis spectroscopy were utilized to characterize the prepared tungsten oxide. Nitrogen adsorption/desorption analysis demonstrated the formation of mesoporous structure with the specific surface area of 67 m2/g and pore size of ~ 6 nm after calcination at 500 oC for 1 h. Microstuctural investigation by field emission scanning electron microscopy images revealed the existence of spherical morphology for the prepared mesoporous tungsten oxide powder. X-ray diffraction analysis confirmed the formation of orthorhombic crystalline structure. In addition, the calculated energy band gap of the calcined product was found to be 2.60 eV. Further, photocatalytic activity of the synthesized crystalline powder was verified for Rhodamine B degradation, giving rise to 79% dye removal from aqueous solution with 6 mg/L concentration under ultraviolet irradiation.Graphical Abstract

Three-dimensionally interconnected porous boron nitride foam derived from polymeric foams

In this work, for the first time, we report the successful synthesis of three-dimensionally interconnected porous boron nitride foams (BNFs) with a high degree of crystallinity using porous sacrificial polymeric hard templates. Ammonia borane/CTAB solution were infiltrated inside highly porous preforms of poly(styrene-co-divinylbenzene) (PS), poly(acrylonitrile-co-divinylbenzene) (PAN) and poly(ethylhexyl acrylate-co-divinylbenzene) (PEHA) made using a high internal phase emulsion process. These were later subjected to pyrolysis under an ammonia atmosphere at the rather low temperature of 1150 °C for 90 minutes. The obtained products were characterized using X-ray diffraction, Fourier transformed infrared spectroscopy, N2 sorption analysis, scanning electron microscopy, scanning transmission electron microscopy and high resolution transmission electron microscopy (HR-TEM). The synthesized BNFs closely replicated and retained the open-cellular interconnected microstructure of the polymeric templates. The HR-TEM results revealed the formation of highly crystalline BN stack layers in small domains. The prepared BNF using the PS template showed superhydrophobic behavior which was typical for all of the prepared samples, with a water contact angle of ∼144° and a high adsorption capacity of 1800% for used engine oil.

One pot synthesis of mesoporous boron nitride using polystyrene-b-poly(ethylene oxide) block copolymer

We report a successful synthesis of Mesoporous BN (MBN) powder through a facile one-pot synthesis strategy. In this respect, laboratory made block copolymer, polystyrene-b-poly(ethylene oxide) (PS-b-PEO) was used as structure directing agent and ammonia borane was used as BN precursor, respectively. Various characterization techniques such as X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM) and N2 sorption analysis were used to characterize different properties of the synthesized MBN powder. The formation of turbostratic boron nitride with wormlike pores (20 nm) was confirmed by XRD and TEM results. N2 sorption analysis of the obtained MBN sample exhibited a high specific surface area of 326 m2 g−1 and a pore volume of 0.5 m3 g−1.

Two-dimensional assemblies of ultrathin titanate nanosheets for lithium ion battery anodes

Ultrathin titanate nanosheets of 0.5 nm thickness were successfully synthesized from the non-hydrolytic sol–gel reaction of tetraoctadecyl orthotitanate via a heat-up method. The synthesized nanosheets were easily assembled to be layer structures by being reacted with hydroxide ions in basic solutions such as LiOH, NaOH, and KOH. The hydrophobic surface of the titanate nanosheets was also modified to be a hydrophilic surface through an assembly process. The layer structured nanosheets were employed as anode materials for lithium ion batteries to visualize fast charging and discharging effects utilizing 2D structured electrodes, and stable cycling induced the mechanically stable layered structure. The ultrathin morphology of the 2D titanate electrodes affected not only the diffusion path of Li ions but also the reaction mechanism from the insertion reaction of the crystal interior to the surface reaction. Furthermore, the electrodes of the layer structured nanosheets had superior cycling and rate performances.

Facile synthesis of nanostructured carbon nanotube/iron oxide hybrids for lithium-ion battery anodes

Nanostructured carbon nanotubes/iron oxide hybrids (CNIOHs) were synthesized by a scalable Bake-Break-Mix process which involves three simple steps. Porous rod-like iron oxide arrays were first synthesized via the decomposition of iron(II) oxalate dihydrate at 300 °C for 5 h. The prepared rod-like structures were simply a well-organized alignment of numerous iron oxide nanoparticles. Breaking these rod-shaped iron oxide arrays into well-dispersed nanoparticles was accomplished by ultrasonication. Finally, single-wall carbon nanotubes were added to the suspension during sonication which allowed the dispersed iron oxide nanoparticles to adsorb to the surface resulting in the nanostructured CNIOHs. CNIOHs were employed as anode materials and showed excellent capacity, cyclic stability and rate capability.

Modulated large-pore mesoporous silica as an efficient base catalyst for the Henry reaction

In this study, mesoporous silica materials with tuned pores and surface areas were successfully synthesized by adjusting the amount of applied hexane and controlling the hydrothermal temperature. The synthesized silica materials were then functionalized by an amine group to produce solid base catalysts and be applicable as efficient heterogeneous base catalysts for the Henry reaction. The mesoporous silica catalysts possessing large-pores and surface area expose their active catalytic sites and thereby improve contacts with reactants fulfilling the reactions expeditiously in comparison with solid base catalysts possessing small-pores and surface area. The results indicated that the yield of the products is significantly dependent on the structure of the applied solid base catalysts. The modulated large-pore solid base catalysts presented high catalytic activity in Henry reactions and could be reused for five consecutive cycles.