Rational design and construction of novel nanostructures with outstanding functions, and investigation on the relationship between their structures and properties have continuously been intriguing but are still challenging now. In this work, 1D TiO₂(B) hierarchitectures with epitaxial {100} and {010} high-energy-facetted ultrathin 2D nanosheets that are parallel to the c-axis are demonstrated for the first time. These hierarchitectures show much improved photochemical properties as compared with the nanoparticles and nanowires as well as the physical mixture of nanosheets and nanowires. These include photodegradation of methyl orange and water splitting, due to the remarkably increased surface area and active sites, and enhanced separation and transport of charge carriers. The findings reported here may inspire the engineering of highly active nanostructures for energy and environment related applications.

Transition metal dichalcogenides (TMDs, such as MoS₂, WS₂ and MoSe₂) with lamellar structures have attracted tremendous attention owing to their similar structure to graphite. However, two-dimensional (2D) TMD nanomaterials display a strong tendency to restack and condense, which leads to a marked decrease of performance in their applications. In this study, we report the synthesis of TMDs by using polyoxometalates (POMs) as tungsten or molybdenum precursors. Hierarchical TMDs with novel structures can be formed below 200 °C, including WS₂ rods, MoS₂ rods and MoSe₂ hollow spheres. All of these structures assembled from the corresponding nanosheets. Meanwhile the epitaxial growth of noble metal nanoparticles (NPs) on TMDs could be achieved very easily. The obtained Pt/WS₂ and Pt/MoS₂ hybrids were highly active and durable HER catalysts. In addition, the Pt NPs on the surface of TMDs could improve the HER activity sharply, which was likely due to the synergistic effect between Pt NPs and MoS₂ rods.

The miniaturization of metal–organic-framework (MOF) crystals to the nanoscale brings enhanced or novel properties and fulfils specific application needs. The focus here is on a kind of nanoMOF with special configurations and outstanding properties – the hollow structure. Firstly recent advances on the synthesis of MOF hollow nanostructures are introduced. Then, a novel approach based on a heterometallic system is highlighted, by which the facile synthesis of well-defined hollow MOF structures with high complexity is achieved. Moreover, MOF hollow nanostructures are emphasized as hosts/shell materials to incorporate functional catalysts that show dramatically enhanced performances in gas-involved reactions due to their inherent gas-absorption/storage properties.

Edges are special sites in nanomaterials. The atoms residing on the edges have different environments compared to those in other parts of a nanomaterial and, therefore, they may have different properties. Here, recent progress in nanomaterial fields is summarized from the viewpoint of the edges. Typically, edge sites in MoS₂ or metals, other than surface atoms, can perform as active centers for catalytic reactions, so the method to enhance performance lies in the optimization of the edge structures. The edges of multicomponent interfaces present even more possibilities to enhance the activities of nanomaterials. Nanoframes and ultrathin nanowires have similarities to conventional edges of nanoparticles, the application of which as catalysts can help to reduce the use of costly materials. Looking beyond this, the edge structures of graphene are also essential for their properties. In short, the edge structure can influence many properties of materials.

Metal-organic frameworks (MOFs) are potentially useful molecular materials that can exhibit structure flexibilities induced by some external stimuli. Such structure transformations can furnish MOFs with improved properties. The shape-controlled growth of MOFs combined with crystal-structure transformation is rarely achieved. Herein, we demonstrate the synthesis of hierarchical Zn/Ni-MOF-2 nanosheet-assembled hollow nanocubes (NAHNs) by a facile surfactant-free solvothermal approach. The unique nanostructures undergo crystal-structure transformation from Zn/Ni-MOF-5 nanocubes to Zn/Ni-MOF-2 nanosheets, which is analogous to the dissolution and recrystallization of inorganic nanocrystals. The present synthetic strategy to fabricate isostructural MOFs with hierarchical, hollow, and bimetallic nanostructures is expected to expand the diversity and range of potential applications of MOFs.

Metal–organic frameworks (MOFs) have demonstrated great potentials in a variety of important applications. To enhance the inherent properties and endow materials with multifunctionality, the rational design and synthesis of MOFs with nanoscale porosity and hollow feature is highly desired and remains a great challenge. In this work, the formation of a series of well-defined MOF (MOF-5, Fe^II-MOF-5, Fe^III-MOF-5) hollow nanocages by a facile solvothermal method, without any additional supporting template is reported. A surface-energy-driven mechanism may be responsible for the formation of hollow nanocages. The addition of pre-synthesized poly(vinylpyrrolidone)- (PVP) capped noble-metal nanoparticles into the synthetic system of MOF hollow nanocages yields the yolk–shell noble metal@MOF nanostructures. The present strategy to fabricate hollow and yolk–shell nanostructures is expected to open up exciting opportunities for developing a novel class of inorganic–organic hybrid functional nanomaterials.

Multidimensional nano-heterostructures (NHSs) that have unique dimensionality-dependent integrative and synergic effects are intriguing but still underdeveloped. Here, we report the first helical 1D/2D epitaxial NHS between CdS and ZnIn₂S₄. Experimental and theoretical studies reveal that the mismatches in lattice and dangling bonds between 1D and 2D units govern the growth procedure. The resulting well-defined interface induces the delocalized interface states, thus facilitate the charge transfer and enhance the performance in the photoelectrochemical cells. We foresee that the mechanistic insights gained and the electronic structures revealed would inspire the design of more complex 1D/2D NHSs with outstanding functionalities.

Metal-organic frameworks (MOFs) are potentially useful molecular materials that can exhibit structure flexibilities induced by some external stimuli. Such structure transformations can furnish MOFs with improved properties. The shape-controlled growth of MOFs combined with crystal-structure transformation is rarely achieved. Herein, we demonstrate the synthesis of hierarchical Zn/Ni-MOF-2 nanosheet-assembled hollow nanocubes (NAHNs) by a facile surfactant-free solvothermal approach. The unique nanostructures undergo crystal-structure transformation from Zn/Ni-MOF-5 nanocubes to Zn/Ni-MOF-2 nanosheets, which is analogous to the dissolution and recrystallization of inorganic nanocrystals. The present synthetic strategy to fabricate isostructural MOFs with hierarchical, hollow, and bimetallic nanostructures is expected to expand the diversity and range of potential applications of MOFs.

Metal–organic frameworks (MOFs) have demonstrated great potentials in a variety of important applications. To enhance the inherent properties and endow materials with multifunctionality, the rational design and synthesis of MOFs with nanoscale porosity and hollow feature is highly desired and remains a great challenge. In this work, the formation of a series of well-defined MOF (MOF-5, Fe^II-MOF-5, Fe^III-MOF-5) hollow nanocages by a facile solvothermal method, without any additional supporting template is reported. A surface-energy-driven mechanism may be responsible for the formation of hollow nanocages. The addition of pre-synthesized poly(vinylpyrrolidone)- (PVP) capped noble-metal nanoparticles into the synthetic system of MOF hollow nanocages yields the yolk–shell noble metal@MOF nanostructures. The present strategy to fabricate hollow and yolk–shell nanostructures is expected to open up exciting opportunities for developing a novel class of inorganic–organic hybrid functional nanomaterials.

Multidimensional nano-heterostructures (NHSs) that have unique dimensionality-dependent integrative and synergic effects are intriguing but still underdeveloped. Here, we report the first helical 1D/2D epitaxial NHS between CdS and ZnIn₂S₄. Experimental and theoretical studies reveal that the mismatches in lattice and dangling bonds between 1D and 2D units govern the growth procedure. The resulting well-defined interface induces the delocalized interface states, thus facilitate the charge transfer and enhance the performance in the photoelectrochemical cells. We foresee that the mechanistic insights gained and the electronic structures revealed would inspire the design of more complex 1D/2D NHSs with outstanding functionalities.

Hollow structures have attracted ever-growing interest owing to their various excellent properties. However, a facile strategy for their fabrication is still desired. Herein, PdPt alloy with three different morphologies, that is, cubes, hollow cubes, and truncated octahedrons, is synthesized by using a one-pot, template-free method. The mechanism and dynamics of this system is also studied in detail. In particular, the hollow cubic structure represents enhanced catalytic activity in both coupling reactions and in the electrochemical oxidation of formic acid.

Palladium is a key catalyst invaluable to many industrial processes and fine-chemical synthesis. Although recent progress has allowed the synthesis of Pd nanoparticles with various shapes by using different techniques, the facile synthesis of Pd nanocrystals and turning them into a highly active, selective, and stable catalyst systems still remain challenging. Herein, we report the highly selective one-pot synthesis of monodisperse Pd cluster nanowires in aqueous solution; these consist of interconnected nanoparticles and may serve as highly active catalysts because of the enrichment of high index facets on the surface, including {443}, {331}, and {221} steps. For the first time, carbon nanotube and γ-Al₂O₃ immobilized Pd cluster nanowires showed highly enhanced catalytic performance in the liquid-phase selective hydrogenation of cinnamaldehyde and gas-phase hydrogenation of 1,3butadiene relative to immobilized Pd icosahedra and nanocubes, as well as commercial Pd catalysts.

The size-dependent surface activity of titania was illustrated through the formation of ultrafine nanocrystals with clean surfaces. It was demonstrated that, when the size of the nanocrystals was small enough, their surface activity could be significantly enhanced, as evidenced by the formation of transparent macroassemblies, their increased dispersity in various solvents, the facile modification of their surface by organic molecules at room temperature, their strong visible-light absorption through coordination with peroxide, and highly enhanced photocatalytic performance.

It was found that calcium carbonate (CaCO₃) and hydroxyapatite (Ca₁₀(OH)₂(PO₄)₆), which are two crucial constituents of the most abundant minerals in nature and very important bioinorganic components in the tissues of mineralizing organisms, can form solid solutions in a wide range of PO₄³⁻/CO₃²⁻ (P/C) ratios at low temperature when prepared as ultrathin nanowire structures. This is due to the special reactivity of ultrasmall nanocrystals, which can effectively lower the synthetic temperature and promote the formation of solid solutions. The as-prepared ultrathin nanowires with suitable P/C ratios presented strong blue luminescence due to the existence of abundant defects strengthened by CO₃²⁻. If used as the matrix, the as-prepared ultrathin nanowires demonstrated bright green or red luminescent properties when doped with Tb³⁺ or Eu³⁺ ions, and simultaneously retained their original morphologies. These three kinds of fluorescent nanowires could reproduce a full range of luminescence colors based on additive color mixtures of the three primary colors (red, green, and blue). In addition, under the same reaction system, ultrafine rare-earth-doped (Ce³⁺, Tb³⁺, Eu³⁺) nanowires (about 1 nm in diameter) were synthesized by using a one-step hydrothermal process, which further pushed the size of the Ca-PO₄-CO₃ nanobuilding blocks to one unit cell region. These ultrafine nanowires displayed excellent film-forming properties and the ability to absorb UV radiation.

MoO₃ has a unique rigid double-layer structure, which makes it a real challenge to prepare nanotubular structures. The controlled synthesis of MoO₃ single-walled nanotubes (SWNTs) is achieved through a cluster-based self-assembly route on the dodecanethiol/water interface. Various factors are studied at length, including precursor type, reaction time, temperature, pH value, and their influence on the morphology of products. The concept of “self-assembly—from simple clusters to nanostructures” is proposed here based on preliminary results from the synthesis of MoO₃ SWNTs, which provides a new aspect for traditional synthetic chemistry of nanomaterials and polyoxometalates.

Monodisperse fullerene-like polyoxometalate-based microspheres are synthesized using a single-phase approach which is quick, easier to control surfactant to polyoxometalate (POM) molar ratios and result in better control over the size-distribution range. Noble-metal nanocrystals are successfully incorporated in the surfactant encapsulated complex multilayered spherical assemblies without any change in their layered morphology. Combining the merits of fullerene-like POMs and monodisperse noble metal nanocrystals, these monodisperse hybrid spheres show interesting composition- and size-dependent photochemical properties.