Solid State Chemistry and Inorganic Synthetic Chemistry – Novel Structures and Accurate Syntheses of Inorganic Materials

Abstract

Solid-state chemistry, aimed at uncovering novel functionalities and structures, has been a cornerstone for advancing industries in solid-state materials, energy, and information technologies. In ensuring reproducibility and desired properties of solid-state materials, inorganic synthetic chemistry serves as the foundation for developing innovative techniques to tailor their structures and properties. Recently, the coordinated manipulation of electronic, molecular, crystal, and nanostructures in solid materials has emerged as a leading frontier in inorganic synthetic chemistry. This advancement is fueling the dynamic growth of solid materials research and sparking innovative, unexpected applications. To highlight the latest advancements in these fields, we have put together a Special Issue titled “Solid State Chemistry and Inorganic Synthetic Chemistry – Novel Structures and Accurate Syntheses of Inorganic Materials”. This collection includes 4 reviews and 19 research articles from prominent scientists with their valuable insights.

Meticulously regulating the electronic structure of materials profoundly influences their physicochemical properties, leading to the emergence of innovative optical, electrical, and magnetic characteristics in solid materials. Prof. Feng Shouhua's group led the way in synthesizing trivalent crystals through transition metal disproportionation in the perovskite system. They uncovered an element with triple valence states in a crystal, showcasing its functionality as an atomic-scale p-n junction and introducing a novel concept of an atomic-scale p-n junction globally. In a new contribution, Yaowen Zhang et al. (smtd.202400539) develope a range of multivalent manganate perovskites using a hydrothermal approach, doping multiple elements at the A-site. This allows manganese atoms with different valence states to be arranged orderly at the B site. The ordered sequence of Mn(III), Mn(IV), and Mn(V) enhances the formation of charge transfer pathways, thus influencing the photodynamic characteristics of the samples. Ran An et al. (smtd.202301577) incorporate Tm³⁺ ions as modulators into pure Er³⁺-based upconversion luminescence crystals. This strategic addition allows for precise regulation of the photon transition processes between the modulator and activator ions, resulting in varied emission colors from the same activator when subjected to adjustable excitation conditions. Zhi-Gang Li et al. (smtd.202301662) reveal that the electronic states of organic ligands exhibiting conjugate effects in lead halide perovskites can reach the band edges. As a result, these band-edge carriers are not confined solely to the inorganic layers; instead, they interact with molecular states within the barrier, leading to enhanced coupling with phonon modes and ultimately producing broadband emission. Yanyan Li et al. (smtd.202400003) utilize two distinct solvents to synthesize lead-free Sb-based organic-inorganic hybrid Na₃SbBr₆(L)₆ (where L = C₂H₆OS and C₄H₈OS) single crystals, which exhibit broad emission spectra and extended lifetimes. These compounds can reversibly interconvert with alterations in both their emission properties and crystal structures through the addition or removal of organic molecules within the crystals. Edlind Lushaj et al. (smtd.202301541) have outlined a straightforward and efficient synthetic method for producing pure nickel hexacyanoferrate nanocubes, a derivative of Prussian blue, characterized by a well-defined crystalline structure along with improved photocatalytic and electrochemical performance suitable for large-scale wastewater treatment applications. Xinyue Chen et al. (smtd.202301774) successfully synthesize boron- and nitrogen-doped nanocrystalline diamond using chemical vapor deposition on Ti and Ti/Ta interlayers that were sputtered onto silicon substrates. This research not only illuminates the complex interplay between interlayer composition, charge transfer mechanisms, and electrochemical behavior but also highlights how customized interlayer designs can enhance functionalities in diamond-based electrochemical devices. Zitong Wang et al. (smtd.202301633) provide a comprehensive summary of the research progress of metal halide perovskites and perovskite analogue compounds via the thermal evaporation strategy, with a particular focus on the thin-film fabrication, device applications in solar cells, and other emerging optoelectronics. They also provide an overview of future opportunities for both fundamental research and commercialization via the thermal evaporation method.

Precise control over molecular structure showcases the versatility of chemical synthesis methods, unlocking a diverse range of transformations for the multifaceted applications of materials. Prof. Yuliang Li's group proposed a new method of surface catalytic coupling of solid-liquid two-phase copper, and graphdiyne was obtained by this chemical synthesis method in 2010 for the first time, opening up a new field of carbon materials. Graphdiyne has emerged as a vibrant area of research, leading to significant advancements across various domains such as catalysis, energy, optoelectronics, life science, and information intelligence. Furthermore, Xiaonan Zhang et al. (smtd.202301571) outline the current research achievements regarding the controlled formation of multiscale metallic interfaces on graphdiyne. Synthetic strategies for interface regulation, as well as the correlation between the structure and performance, are presented. The promising application potential of graphdiyne-based substances are also demonstrated. Another key feature of nano- and low dimensional inorganic solids is the quantum confinement effect. When the size of a material is reduced to the nanoscale, the movement of electrons and holes becomes restricted, leading to changes in the energy levels and electronic properties, which are different from those of the bulk materials. Another important aspect of nano- and low dimensional inorganic solids is their large surface-to-volume ratio. This leads to enhanced surface reactivity and interaction with the surrounding environment. Jiaqi Wang et al. (smtd.202301602) focus on the precise synthesis of 2D/2D MXene-based catalysts. They conduct thorough studies on the internal interactions and structure-performance relationships of these catalysts to enhance their potential for electrocatalytic water splitting applications. Eunsoo Lee et al. (smtd.202301782) outline the unique features of nanoscale confined 2D metal compounds, their synthetic challenges, recent key reports of electrocatalytic applications, and future research directions. Chen Wang et al. (smtd.202301804) prepare ultrathin BiVO₄-Au-Cu₂O nanosheets which provided more reaction sites and reduced the charge carrier transfer length to the reaction sites. The Au nanoparticles promote the formation of the Z-scheme heterojunction, and enhance the light absorption and excitation of hot electrons. The synergism of the abovementioned properties endowed the BiVO₄-Au-Cu₂O nanosheets with satisfactory photocatalytic activity in the degradation of tetracycline. Chao Hsuan Sung et al. (smtd.202400245) have developed Ni-based polymer/carbon nanofibers and uncovered the nucleation process of nickel that occurs at the beginning of polymer scaffold decomposition, followed by growth mechanisms including surface diffusion, aggregation, coalescence, and evaporation condensation. The nanofibers exhibit good gas sensing performance against NH₃. Mengying Huang et al. (smtd.202301652) construct a series of composite catalysts by supporting phthalocyanine Co(II) with different peripheral substituents onto the surface of the multi-walled carbon nanotubes. The influence of the peripheral substituents on the local electronic structure of Co atoms in these catalysts are disclosed, would be helpful for developing Co-N₄ based catalysts with promising catalytic performance toward CO₂ reduction reaction. Weikang He et al. (smtd.202301167) create a flexible electrode featuring a three-dimensional heterostructure composed of sulfur-doped NiMn-layered double hydroxide (LDH) nanosheets combined with sulfur-doped NiCo-LDH nanowires. The resulting asymmetric supercapacitor demonstrates both high energy density and impressive power density.

The design of crystal structures mirrors human comprehension, acknowledgment, and utilization of periodic arrangements, giving rise to a collection of ideal architectural marvels on a microscopic scale. Prof. Xiaoming Chen's group created a metal-organic framework (MOF) (metal-azolate framework-4, MAF-4, also known as ZIF-8) featuring a natural molecular sieve structure with permanent pores formed by imidazole derivatives and zinc ions, sparking a resurgence in MOF research exploring their outstanding capabilities in adsorption, separation, catalysis, and other areas. The fusion of metal complexes and porous materials yields enhanced functional materials, boosting catalytic performance and selectivity. The porous structure enables confinement effects, regulating reactant access to metal centers. These materials hold promise for gas storage and separation applications. Xiongkai Tang et al. (smtd.202400040) report a new synthetic strategy to access atomically precise Pd nanoclusters containing low valence Pd centers. By utilizing specially designed chiral pyridine-imine ligands, they successfully obtain chiral Pd₄ nanoclusters. This synthetic technique is versatile, accommodating a broad range of ligands and enabling the straightforward production of phosphine-ligated Pd nanoclusters. Qi-Sheng Huang et al. (smtd.202301705) prepare a new hyperbranched metal–organic cluster (MOC) crosslinker containing up to 16 vinyl groups by a straightforward coordination reaction. Hyper-crosslinked polymer elastomers can be easily obtained via a polymerization reaction between MOC and monomers, which exhibit improved mechanical strengths, creep-resistance, and humidity-stability. Avneet K. Ramana et al. (smtd.202301703) describe the crystal structures of four coordination polymers formed from Sn(II) ions and polydentate carboxylate ligands. The polymorphism for the Sn(II) materials is in part due to the asymmetric coordination of the metal cation with its 5s² electron pair. Wan-Feng Xiong et al. (smtd.202301807) design a unique Cu/UIO-Br interface for the selective production of C₂₊ products in CO₂ reduction reaction, wherein the Cu(111) plane was modified effectively by the O and Br atoms from halogenated zirconium 1,4-dicarboxybenzene MOF (UIO-66). The UIO-66-Br not only provided ideal support for Cu nanoparticles uniform distribution, but also acted as a molecular reservoir for Br and O atoms. Chengcheng Dong et al. (smtd.202301302) investigate the hydroboration reaction involving commercially available borane dimethyl sulfide complex BH₃∙SMe₂ with multi-alkynes under mild conditions, leading to the formation of new Lewis acidic porous alkenyl borane polymers (PABPs), which achieve 100% atom efficiency in their synthesis. These boron-containing porous organic polymers exhibit high surface areas and well-defined Lewis acidic B-centers, providing PABPs with exceptional capabilities for capturing volatile triethylamine and pyridine.

Hollow/core-shell structures have gained attention as highly effective materials due to their distinctive architectures and outstanding characteristics. The accurate synthesis of these structures is a critical aspect that determines their performance and potential applications. A significant instance is the advent of hollow multishelled structure (HoMS). The emergence of HoMS gained attention in 2004. Despite their appealing properties, intricate synthesis steps initially impeded progress. Porf. Dan Wang's group overcame this challenge by precisely regulating HoMS synthesis through concentration waves, uncovering their distinctive temporal-spatial ordering. Subsequently, the synthesis and utilization of HoMS have thrived. In a recent breakthrough, Qian Xiao et al. (smtd.202301664) have successfully fabricated the amorphous coordination polymers (CP)-composited HoMS with controlled shell number through precise control of the decomposition of MOF-235 and the formation of CP shells triggered by alkaline conditions. Fe-CP HoMS loaded with doxorubicin is utilized for synergistic chemotherapy and chemodynamic therapy, offering excellent responsive drug release capability. Yilei He et al. (smtd.202301560) create metal phosphide core-shell heterostructures supported by carbon nanosheets through the processes of carbonization and phosphidation of a 2D Ni-MOF precursor. This core-shell nanostructure enhances accessibility to active sites and improves durability, while the underlying 2D carbon nanosheet helps prevent aggregation of the heterostructures and promotes mass transfer. The optimization of geometric and electronic configurations in the Ni/Ni₂P heterostructure favors the adsorption of OOH^* intermediates. These attributes contribute to the exceptional performance of Ni@Ni₂P/C nanosheets in facilitating a two-electron pathway for oxygen reduction reactions aimed at H₂O₂ production. Lei Jin et al. (smtd.202301695) develop eco-friendly and Ag, Mn co-doped ZnIn₂S₄/ZnS quantum dots using a facile one-pot core/shell synthesis approach. Their properties, including visible light transparency, significant Stokes shift, and high photoluminescence quantum yield make these Ag, Mn: ZnIn₂S₄/ZnS quantum dots suitable luminophores for transparent colorless LSC applications. Qilin Wei et al. (smtd.202301709) report a general synthesis protocol involving uniform deposition of metal hydroxide on silica nanospheres with a controlled manner at appropriate solution pH values followed by a thermal reduction in forming gas at elevated temperatures. The successful synthesis of silica nanospheres supported ultrafine metal nanoparticles (ufMNPs) below 5 nm with clean surfaces and enhanced optical absorption is promising for exploring the photocatalytic properties of ufMNPs.

This special issue of Small Methods serves as a platform to showcase significant advancements in solid-state chemistry and inorganic synthetic chemistry from research teams around the globe. We hope that this special issue will promote exchanges and cooperation between researchers and practitioners in various fields. We extend our sincere gratitude to all the authors for their outstanding contributions, which truly represent the cutting edge of progress in this particular field. We would like to express our heartfelt gratitude to the editorial team of Small Methods, particularly Dr. Anja Wecker, for supplying us the chance to publish this special issue.

The authors declare no conflict of interest.