Thiosalicylic-Acid-Mediated Coordination Structure of Nickel Center via Thermodynamic Modulation for Aqueous Ni-Zn Batteries

Uniquely functional nanocomplexes with rich coordination environments are critical in energy storage. However, the construction of structurally versatile nanocomplexes remains challenging. In this study, a nickel-based complex with structural variations is designed via thermodynamic modulation using a dual-ligand synthesis strategy. A nickel-based nanomaterial (NiSA-SSA-160) with a large specific surface area is synthesized around the competing coordination of the host and guest molecules that differ in terms of the chemical properties of the O and S elements. Concurrently, the coordination environment of NiSA-SSA-160 is investigated via X-ray absorption fine structure spectroscopy. The thiol functional groups synergistically induced an electron-rich Ni structure, thus increasing the electron density of the central atom. The electrochemical performance of an assembled NiSA-SSA-160//Zn@CC battery is shown to improve significantly, with a maximum energy density of 0.54 mWh cm-2 and a peak power density of 49.49 mW cm-2. This study provides a new perspective regarding coordination transformations and offers an idea for the design of functionally rich nanomaterials.

Synthesis Strategy Guided by Decision Tree for Morphology Control of Metal Phosphonates

The morphology control of metal phosphonates is always a difficulty because there are many challenges derived from the complexity of crystallization and the multivariable synthesis system. Responding to challenges, we propose a synthesis strategy guided by a decision tree for morphology control of metal phosphonates, through which directional design of the morphology-controlled synthesis can be realized. Specifically, any one synthetic condition involving the synthesis of metal phosphonates can be regarded as a decision problem to construct a binary decision tree. By means of the classification principle of the binary decision tree, the samples synthesized under the boundary value of each synthesis condition are classified based on crystal phase and morphology. The key synthetic conditions determining crystal phase and morphology can be precisely screened out to serve as decision nodes for the binary decision tree and are also rapidly optimized by the recursion level by level, whereas others cannot. Here, the β-polymorph of copper phenylphosphonate (β-CuPP) is selected as an example to elaborate the decision-tree-guided synthesis strategy for morphology control of metal phosphonates. From the constructed binary decision tree, it is clear that the right amount of methanol in the solvent is vital to obtain β-phase of CuPP, whereas the reactant concentration, pH value, and reaction time are important for morphology and phase transformation. Under the optimal synthetic conditions screened out by the binary decision tree, β-CuPP can thus be controlled to be hierarchically flower-like microsphere morphology through either the direct synthesis route or the solid-to-solid phase transformation route. This research work confirms that the decision-tree-guided synthesis is highly efficacious for the morphology control of metal phosphonates. Furthermore, the morphology-controlled synthesis guided by a decision tree may provide some valuable inspiration for morphology control of metal-organic frameworks (MOFs) and even coordinate compounds.

Regulating Intramolecular Electron Transfer of Nickel-Based Coordinations through Ligand Engineering for Aqueous Batteries

The integration of electronic effects into complexes for the construction of novel materials has not yet attracted significant attention in the field of energy storage. In the current study, eight one-dimensional (1D) nickel-based salicylic acid  complexes (Ni-XSAs, X = pH, pMe, pMeO, mMe, pBr, pCl, pF, and pCF3 ), are prepared by ligand engineering. The coordination environments in the Ni-XSAs are explored using X-ray absorption fine structure spectroscopy. The charge transfer of the complexes is modulated according to the difference in the electron-donating ability of the substituents, in combination with frontier orbital theory. Furthermore, density functional theory is used to investigate the effect of the substituent position on the electronic properties of the complexes. Ni-mMeSA exhibits better electrical conductivity than Ni-pMeSA. The electrochemical performance of Ni-mMeSA as an aqueous battery cathode is remarkably improved with a maximum energy density of 0.30 mWh cm-2 (125 Wh kg-1 ) and a peak power density of 33.72 mW cm-2 (14.03 kW kg-1 ). This study provides ideas for the application of new coordination chemistry in the field of energy materials science.

Nanoporous Metal Phosphonate Hybrid Materials as a Novel Platform for Emerging Applications: A Critical Review

Nanoporous metal phosphonates are propelling the rapid development of emerging energy storage, catalysis, environmental intervention, and biology, the performances of which touch many fundamental aspects of portable electronics, convenient transportation, and sustainable energy conversion systems. Recent years have witnessed tremendous research breakthroughs in these fields in terms of the fascinating pore properties, the structural periodicity, and versatile skeletons of porous metal phosphonates. This review presents recent milestones of porous metal phosphonate research, from the diversified synthesis strategies for controllable pore structures, to several important applications including adsorption and separation, energy conversion and storage, heterogeneous catalysis, membrane engineering, and biomaterials. Highlights of porous structure design for metal phosphonates are described throughout the review and the current challenges and perspectives for future research in this field are discussed at the end. The aim is to provide some guidance for the rational preparation of porous metal phosphonate materials and promote further applications to meet the urgent demands in emerging applications.