Advances in morphology-controlled alumina and its supported Pd catalysts: synthesis and applications

Alumina materials, as one of the cornerstones of the modern chemical industry, possess physical and chemical properties that include excellent mechanical strength and structure stability, which also make them highly suitable as catalyst supports. Alumina-supported Pd-based catalysts with the advantages of exceptional catalytic performance, flexible regulated surface metal/acid sites, and good regeneration ability have been widely used in many traditional chemical industry fields and have also shown great application prospects in emerging fields. This review aims to provide an overview of the recent advances in alumina and its supported Pd-based catalysts. Specifically, the synthesis strategies, morphology transformation mechanisms, and structural properties of alumina with various morphologies are comprehensively summarized and discussed in-depth. Then, the preparation approaches of Pd/Al2O3 catalysts (impregnation, precipitation, and other emerging methods), as well as the metal-support interactions (MSIs), are revisited. Moreover, Some promising applications have been chosen as representative reactions in fine chemicals, environmental purification, and sustainable development fields to highlight the universal functionality of the alumina-supported Pd-based catalysts. The role of the Pd species, alumina support, promoters, and metal-support interactions in the enhancement of catalytic performance are also discussed. Finally, some challenges and upcoming opportunities in the academic and industrial application of the alumina and its supported Pd-based are presented and put forward.

Anchoring copper nanoclusters to Al2O3 microsphere for dual-mode analysis of N-acetyl-β-D-glucosaminidase and information encryption

Herein, we attempted to confine copper nanoclusters (CuNCs) with alumina (Al2O3) as the matrix (Al2O3@CuNCs), which effectively circumvented the drawbacks of CuNCs (such as weak photoluminescence and low quantum yield). Al2O3@CuNCs demonstrated sensitive response to p-nitrophenol, the catalytic product of N-acetyl-β-D-glucosaminidase (NAG) on account of the inner filter effect and dynamic quenching effect. In light of this, a novel assay was created to identify NAG, a critical indicator of diabetic nephropathy. Additionally, a portable and instrument-free sensing platform mainly consisting of a smartphone, a cuvette, a cuvette holder, a dark box and a 365 nm UV lamp was developed for the quantitative detection of NAG. The as-prepared material was also utilized in anti-counterfeiting and information encryption based on their excellent optical properties and sensitive response to the catalyzed product of NAG. This work advanced potential applications of CuNCs composites in the areas of portable, multi-mode biosensing, anti-counterfeiting and information encryption.

Pyrolysis of Al-Based Metal-Organic Frameworks to Carbon Dot-Porous Al2 O3 Composites With Time-Dependent Phosphorescence Colors for Advanced Information Encryption

Phosphorescent materials with time-dependent phosphorescence colors (TDPCs) have great potential in advanced optical applications. Synthesis of such materials is attractive but challenging. Here, a series of carbon dot-porous Al2 O3 composites exhibiting distinctive TDPC characteristics is prepared by high-temperature pyrolysis of Al-based metal-organic frameworks NH2 -MIL-101(Al). The composite synthesized at 700 °C (CDs@Al2 O3 -700) shows an obvious change in phosphorescence color from blue to green after removing the excitation light of 280 nm. Photophysical analysis reveals that two emission centers in CDs, namely carbon core and surface states, are responsible for the short-lived blue phosphorescence (96 ms) and long-lived green phosphorescence (911 ms), respectively. The combination of blue and green phosphorescence with different decay rates triggering the interesting TDPC phenomenon. CDs@Al2 O3 -700 has a significantly high phosphorescence quantum yield of up to 41.7% and possesses an excellent optical stability against water, organic solvents, and strong oxidants, which benefits from the multi-confinement of CDs by the porous Al2 O3 matrix through rigid network, strong space constraint, and stable covalent bonding. Based on the TDPC property, multilevel coding patterns composed of CDs@Al2 O3 are successfully fabricated for advanced dynamic information encryption.

Modified boehmite: a choice of catalyst for the selective conversion of glycerol to five-membered dioxolane

The catalytic activity of WO3@boehmite for the acetalization of glycerol with aromatic aldehydes is described in this article. The catalyst is selective towards dioxolane (up to 96%) with excellent conversion (up to 100%) in selective substrates.

Biomolecule-Assisted Synthesis of Hierarchical Multilayered Boehmite and Alumina Nanosheets for Enhanced Molybdenum Adsorption

The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al₂ O₃ ) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al₂ O₃ nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al₂ O₃ multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al₂ O₃ nanosheets possess high surface areas up to 425 and 371 m²  g^-1 , respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al₂ O₃ multilayered nanosheets exhibit Mo adsorption capacities of 33.1-40.8 mg g^-1 . The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future.

Template-Free Fabrication of Mesoporous Alumina Nanospheres Using Post-Synthesis Water-Ethanol Treatment of Monodispersed Aluminium Glycerate Nanospheres for Molybdenum Adsorption

This work reports the template-free fabrication of mesoporous Al₂ O₃ nanospheres with greatly enhanced textural characteristics through a newly developed post-synthesis "water-ethanol" treatment of aluminium glycerate nanospheres followed by high temperature calcination. The proposed "water-ethanol" treatment is highly advantageous as the resulting mesoporous Al₂ O₃ nanospheres exhibit 2-4 times higher surface area (up to 251 m² g^-1 ), narrower pore size distribution, and significantly lower crystallization temperature than those obtained without any post-synthesis treatment. To demonstrate the generality of the proposed strategy, a nearly identical post-synthesis "water treatment" method is successfully used to prepare mesoporous monometallic (e.g., manganese oxide (MnO₂ )) and bimetallic oxide (e.g., CuCo₂ O₄ and MnCo₂ O₄ ) nanospheres assembled of nanosheets or nanoplates with highly enhanced textural characteristics from the corresponding monometallic and bimetallic glycerate nanospheres, respectively. When evaluated as molybdenum (Mo) adsorbents for potential use in molybdenum-99/technetium-99m (⁹⁹ Mo/^99m Tc) generators, the treated mesoporous Al₂ O₃ nanospheres display higher molybdenum adsorption performance than non-treated Al₂ O₃ nanospheres and commercial Al₂ O₃ , thereby suggesting the effectiveness of the proposed strategy for improving the functional performance of oxide materials. It is expected that the proposed method can be utilized to prepare other mesoporous metal oxides with enhanced textural characteristics and functional performance.

A green surfactant-assisted synthesis of hierarchical TS-1 zeolites with excellent catalytic properties for oxidative desulfurization

Hierarchical TS-1 zeolites with intracrystalline mesopores are synthesized via a green surfactant-assisted route, showing excellent performance in oxidative desulfurization.

Monodispersed hierarchical γ-AlOOH/Fe(OH)3 micro/nanoflowers for efficient removal of heavy metal ions from water

Monodispersed γ-AlOOH/Fe(OH)₃ with hierarchical structures have been prepared, which show an excellent performance for As(v) and Cr(vi) removal.

The preparation of modified boehmite/PMMA nanocomposites by in situ polymerization and the assessment of their capability for Cu2+ ion removal

The addition of nanoboehmite as a nanofiller into the polymer matrix led to the improvement of the thermal properties and increased the active sites of nanocomposites for Cu(ii) removal.

Functional nicotinic acetylcholine receptor reconstitution in Au(111)-supported thiolipid monolayers

The insertion and function of the muscle-type nicotinic acetylcholine receptor (nAChR) in Au(111)-supported thiolipid self-assembled monolayers have been studied by atomic force microscopy (AFM), surface plasmon resonance (SPR), and electrochemical techniques. It was possible for the first time to resolve the supramolecular arrangement of the protein spontaneously inserted in a thiolipid monolayer in an aqueous solution. Geometric supramolecular arrays of nAChRs were observed, most commonly in a triangular form compatible with three nAChR dimers of ∼20 nm each. Addition of the full agonist carbamoylcholine activated and opened the nAChR ion channel, as revealed by the increase in capacitance relative to that of the nAChR-thiolipid system under basal conditions. Thus, the self-assembled system appears to be a viable biomimetic model to measure ionic conductance mediated by ion-gated ion channels under different experimental conditions, with potential applications in biotechnology and pharmacology.

Facile synthesis of pure phase γ-AlOOH and γ-Al2O3nanofibers in a recoverable ionic liquid via a low temperature route

Mesoporous γ-AlOOH and γ-Al₂O₃with fibrous morphology were successfully synthesized by an ionic liquid ([OMim]Br) assisted low temperature precipitation method using aluminum nitrate and ammonia as aluminum source and precipitant, respectively.