This review focuses on recent efforts to enhance photocatalytic activities of metal nanoparticle-mediated photocatalysts through “strong metal-support interaction” (SMSI). Herein, we discuss the fundamentals of “strong metal-support interaction” and the methodology to practice the concept, involving synthesis and characterization techniques. The strengths and limitations of SMSI are also discussed, thus outlining future perspectives.

Abstract

Engineering the composition and geometry of metallic sites has become a popular manner to boost reaction rate and control reaction selectivity in heterogeneous catalysis. Many studies have been devoted to enhancing the stability of metallic nanoparticles during catalytic reactions by dispersion on metal oxide supports such as TiO₂, CeO₂ or Nb₂O₅. These supports not only modulate electronic properties and dispersion/stabilization of metallic nanoparticle but also influence catalytic selectivity, resulting in the so-called “strong metal-support interaction” (SMSI). In this minireview, we outlined the discovery and fundamentals of SMSI, as well as its extensive development over years. In addition, we summarized recent approaches developed to induce the construction of SMSI between different metal nanoparticles and metal oxide supports. Associated characterization microscopic and spectroscopic techniques were emphasized. Despite being a prevalent concept in catalysis, the number of studies on SMSI in heterogeneous photocatalysis has been even in limitation. Herein, we highlighted the beneficial effects of SMSI on boosting photocatalytic activity for CO₂ reduction and H₂ evolution reactions. In general, despite some controversial aspects of the SMSI, this concept offers wide opportunities ahead and encourages researchers to rethink the local active site localization and photocatalyst design.

Schematic diagram of the dominant mechanism of NH₃-SCR reaction on CeCu/MCM-49 catalyst before and after poisoning. The L−H mechanism was dominant before poisoning. However, after alkali metal poisoning, NO_x adsorption on the catalyst is inhibited, so the E−R mechanism dominates.

Abstract

NO_x is a common atmospheric pollutant, and NH₃-SCR technology efficiently purifies it. CeCuO_x binary-oxide nanoparticles were synthesized and loaded onto acid MCM-49 molecular sieve with a large specific surface area to increase acid sites and disperse active sites of the catalyst. The optimized 35 % CeCu/MCM-49 catalyst effectively purified over 80 % of NO_x in the temperature range of 200–500 °C and demonstrated excellent resistance to alkali metals, such as K, Na, and Ca. Even after K poisoning, it still removed over 80 % of NO_x in the range of 200–450 °C. Various characterization methods, including XRD, FT-IR, TEM, and N₂ isotherm adsorption-desorption tests, confirmed the structure of the catalyst remained intact after poisoning with no substance change, nor agglomeration of nanoparticles. NH₃-TPD and H₂-TPR confirmed that the catalyst had effective acidity and redox capacity that were not affected by alkali metals. In-situ DRIFTs showed that the catalytic reaction predominant mechanism shifted from L−H to E−R mechanism after poisoning. This study provides valuable insights into the development of high-performance Ce-based NH₃-SCR catalysts with alkali metal resistance.

Organic solvent nanofiltration (OSN) is an emerging separation technology. Significant efforts have been dedicated to designing and fabricating thin film composite (TFC) membranes for OSN in recent years. The development and utilization of TFC membranes in OSN are paramount in ensuring the permeability of organic solvent and rejection of solute. Additionally, researchers have delved into optimizing preprocessing and post-treatment procedures during preparation. The preparation process has emerged as another avenue for improving the separation performance of TFC membranes. Simultaneously, various supports have been explored to enhance the TFC membranes' performance, including polymer substrates and inorganic substrates, as well as the interlayers between the substrate and the TFC membrane, each with unique advantages and disadvantages, and the choices of support depend on the specific requirements of the intended application. The limitations of conventional membranes could be overcome and thus achieve superior performance via an improved preparation strategy of the TFC membranes. This review presents a comprehensive overview of the preparation process for TFC membranes, including a detailed discussion of the preparation methods, the optimizing processes, and the substrates. Different TFC membranes for the OSN application is further discussed.

Atomically-dispersed heterogeneous metal catalysts can be considered as an “upgraded” version of classical solid metal catalysts. Unlike traditional heterogeneous metallic catalysts that contain nanoparticles or bulk micro-sized transition metal species, the active sites of these novel types of catalysts are atomically distributed on the support’s surface. This provides several advantages compared to classical catalysts such as higher activity and need for just very small amounts of metal precursors for the catalyst preparation. The latter issue is a key point in green chemical processes and of importance to achieve low-cost pathways for industrial-scale synthesis. The atomically dispersed metal sites permit a maximum of metal dispersion and additionally allow to achieve more reproducible heterogeneous catalysts. This review summarizes an overview on breakthrough findings in synthesis, applications and characterization techniques developed in the area of single-atom, dual-atom, single-atom-layer, single-site as well as single-atom nanozyme/enzyme catalysis. The characteristics and properties of each system provide an appropriate understanding for designing a nanomaterial that is optimized for a specific requirement.

Cell membranes with penetrating ion channels have unique pathways for efficient transportation of molecules and ions, providing an excellent model for the construction of high-performance mixed matrix membranes (MMMs). In this minireview, recent advances in the design and construction of MMMs with penetrating subnanochannels as well as their applications in gas separation and ion sieving are discussed in detail.

Abstract

Membrane-based separation technologies are becoming increasingly prominent in many important industrial separation applications. In the past decade, nanoporous materials, as promising filler components for high-performance mixed matrix membranes (MMMs), have seen a boom given the merits of remarkable chemical and structural variability. However, it remains challenging to address the trade-off effect of MMMs between molecular/ionic selectivity and permeability. Biological ion channels that penetrate through cell membranes have provided new insights for the construction of novel structures of MMMs. In recent years, MMMs with cell membrane-like structures have gained much attention and achieved significant progress in the field of separation. In this minireview, recent advances in the design and construction of MMMs with penetrating subnanochannels are summarized. After that, the applications of these MMMs with penetrating subnanochannels in gas separation and ion sieving are highlighted and discussed in detail. Finally, the future developments and challenges for the MMMs with penetrating subnanochannels are prospected.

(EK)₁₀ prevents plasma protein adsorption, and MMP-2-responsive PLGLAG exposes Tat near tumors. A leucine zipper connects (EK)₁₀-PLGLAG-Tat to ELP, creating the environmentally responsive gene carrier (ERGV). ERGV efficiently targets tumors by modifying surface charge in MMP-2 environments, ensuring safe and effective gene delivery.

Abstract

Peptide- and polypeptide-based self-assembling gene delivery systems have received considerable attention owing to their inherent biocompatibility and bioactivity. Gene carriers based on elastin-like polypeptides (ELPs) have been extensively studied because of their controllability and unique temperature responsiveness. The (EK)₁₀-PLGLAG-Tat polypeptide sequence was selected for tumor gene delivery, with ELP serving as the hydrophobic core. In this sequence, a hydration layer can be formed on the surface of the carrier using the zwitterionic peptide segment (EK)₁₀, which helps prevent the nonspecific adsorption of plasma proteins. Additionally, the MMP-2 enzyme-responsive PLGLAG peptide segment is responsible for exposing the cell-penetrating peptide Tat specifically near tumor cells, facilitating the penetration of tumor cells. To introduce (EK)₁₀-PLGLAG-Tat into the self-assembling carrier while ensuring its bioactivity, a leucine zipper ZR/ZE with opposite charges was used to link it to the ELP. Because of its high specificity and low systemic toxicity, the carrier was named environmentally responsive gene carrier (ERGV). Experimental results demonstrated that the ERGV effectively removed (EK)₁₀ in MMP-2 overexpressed environments, altering the surface charge from negative to positive and facilitating ssDNA delivery into tumor cells. These findings highlight the potential of ERGVs as a safe and efficient method for targeted gene delivery to tumors.

Solar hydrogen evolution using N-doped titania photocatalyst has gained significant interest in sustainable energy technologies. Here, we demonstrate the successful and reproducible synthesis of defect-enriched nitrogen-doped ordered mesoporous titania with a well-organized crystalline framework structure and point defects like trapped electrons and Ti³⁺ centers. The resulting materials demonstrate the superior performance owing to a synchronizing effect of the presence of intrinsic defects, efficient charge migration, and enhanced absorbance of light properties.

Abstract

The conversion of solar energy into fuel has gained significant interest, particularly in photocatalytic water splitting, and the materials that efficiently generate hydrogen from water or aqueous solution using solar irradiation are highly desired for the hydrogen economy. Photocatalysts made of N-doped TiO₂ are frequently utilized for breaking of water molecules in the process of generating hydrogen. To achieve this target, a unique defect-induced nitrogen-doped highly organized 2D-hexagonal periodic mesoporous titania, TiO_2-xN_y with a well-crystallized framework is synthesized in a reproducible way using structure-directing agents, e. g., F108, F127, P123, and CTAB. The nitrogen is incorporated into these samples through a facile method involving the calcination of templated materials in an air. A systematic characterization of the resulting ordered mesoporous titania employing a battery of experimental techniques indicates the presence of considerable amounts of intrinsic defects, viz., trapped electrons in oxygen vacancy and/or Ti³⁺ centres via nitrogen-doping in the titania matrix. These defects in turn promote the charge separation of photogenerated excitons, and therefore exhibit excellent photocatalytic activity for the hydrogen evolution reaction as compared to commercial titania such as Aeroxide^®P-25. The superior activity of the N-doped mesoporous TiO₂ is attributed to the synergistic effect of facile charge migration with high carrier density, unique phase composition (bronze and anatase), slow recombination of photo-induced excitons, and enhanced absorbance from ultra-violet to the visible region.

Co(OH)₂ is an excellent bifunctional electrocatalyst for overall water splitting at 1.64 V, which competes with state-of-art couples Pt−C//IrO₂ (1.63 V). A novel preparation method, in-situ fast reduction release/oxidization mechanistic way to obtain a spindle nanosheet electrocatalyst is reported.

Abstract

Water electrolysis focused with electricity or sunlight is one of the sustainable methods to produce hydrogen; this helps to address the global energy demand whereas sluggish OER and HER kinetic barriers hamper this process. Here, we report an earth abundant Co(OH)₂ spindle nanosheet electrocatalyst synthesized via surfactant with boron-assisted release/oxidize mechanistic process and employed it as a bifunctional electrocatalyst (OER/HER) with small overpotential (258 mV/156 mV), low Tafel slope (78 mV dec⁻¹/71 mV dec⁻¹), higher turnover frequency (0.235 s⁻¹/0.100 s⁻¹) and low charge transfer resistance (4.7 Ω). The higher electrochemical active surface area (45 cm²) of the catalyst exploits the potential electrocatalyst nature with overall cell voltage 1.64 V at 10 mA cm⁻².

MOFs and COFs have developed their own construction principles and methodologies. The process of learning and adopting each other's methodologies in structural design and synthesis is an emergent hot area and will be further developed. This view highlights the recent emerging development of a multi-component/reaction strategy for covalent organic framework (COF) synthesis and its application in new MOF synthetic strategy and ligand development.

Abstract

Covalent organic frameworks (COFs) and metal organic frameworks (MOFs) are crystalline porous materials with ordered framework structures. To create diverse framework structures, linkers with different geometries and sizes have been developed over the past decades. However, for more advanced applications, there is a need for continuous pore size control and property development. Researchers are exploring new synthesis methods, building blocks, and processing/fabrication protocols to meet these demands. Multi-component or multiple ligands synthesis has been widely used in the construction of MOF structures, and this synthetic strategy has recently been adopted for COF synthesis and extended to versatile linker designing strategies. This review focuses on the recent development of the multi-component or multi-reaction strategy for COF synthesis, its application in new MOF synthetic strategies, and ligand development.

Silver nanoparticles (Ag-NPs) exhibit the highest efficiency of localized surface plasmon resonance (LSPR) excitation that can be tuned to any wave length in the visible spectrum. Its performance depends to a large extent on its physicochemical characteristics such as size and shape; which, in turn, can be modulated by the selective growth of their crystalline facets. We used a simple direct chemical reduction method with a precise manipulation of seed-mediated growth control through an automated single-phase continuous flow-batch system to induce customized geometries on Ag-NPs. Optimization of the experimental design was carried out from a multivariate analysis, where the height / width ratio of LSPR band was used as response signal. Proposed methodology controls the critical steps in the synthesis of Ag-NPs that modulate their morphology to attain customized surface plasmon resonance in an interval of 380 nm (spherical-shaped nanoparticles) to 925 nm ({111}- faceted prism-shaped nanoplates) absorptions, leading to a versatile platform to extend their potential applications. Although the present work focused on silver nanoparticles, we believe that this methodology can be extended to any free-electron metals.