Threefold Collaborative Stabilization of Ag 14 ‐Nanorods by Hydrophobic Ti 16 ‐Oxo Clusters and Alkynes: Designable Assembly and Solid‐State Optical‐Limiting Application

All-catecholate-stabilized black titanium-oxo clusters for efficient photothermal conversion

The controlled synthesis of titanium-oxo clusters (TOCs) completely stabilized by organic dye ligands with high stability and superior light absorption remains a significant challenge. In this study, we report the syntheses of three atomically precise catechol (Cat)-functionalized TOCs, [Ti2(Cat)2(OEgO)2(OEgOH)2] (Ti2), [Ti8O5(Cat)9(iPrO)4(iPrOH)2] (Ti8), and [Ti16O8(OH)8(Cat)20]·H2O·PhMe (Ti16), using a solvent-induced strategy (HOEgOH = ethylene glycol; iPrOH = isopropanol; PhMe = toluene). Interestingly, the TiO core of Ti16 is almost entirely enveloped by catechol ligands, making it the first all-catechol-protected high-nuclearity TOC. In contrast, Ti2 and Ti8 have four weakly coordinated ethylene glycol ligands and six weakly coordinated iPrOH ligands, respectively, in addition to the catechol ligands. Ti16 is visually evident in its distinctively black appearance, which belongs to black TOCs (B-TOCs) and exhibits an ultralow optical band gap. Furthermore, Ti16 displays exceptional stability in various media/environments, including exposure to air, solvents, and both acidic and alkaline aqueous solutions due to its comprehensive protection by catechol ligands and rich intra-cluster supramolecular interactions. Ti16 has superior photoelectric response qualities and photothermal conversion capabilities compared to Ti2 and Ti8 due to its ultralow optical band gap and remarkable stability. This discovery not only represents a huge step forward in the creation of all-catecholate-protected B-TOCs with ultralow optical band gaps and outstanding stability, but it also gives key valuable mechanistic insights into their photothermal/electric applications.

Heterometallic Polyoxotitanium Clusters as Bifunctional Electrocatalysts for Overall Water Splitting

Incorporating heterometal into titanium-oxygen clusters (TOCs) is an effective way to improve its catalytic activity. Herein, we synthesize three novel heterometallic TOCs with the formula of [Ti₆Cu₂O₇(Dmg)₂(OAc)₄(ⁱPrO)₆][H₂Ti₆Cu₂O₇(Dmg)₂(OAc)₄(ⁱPrO)₈] ({Ti₆Cu₂}), [Ti₈Cu₂O₉(Dmg)₂(OAc)₂(ⁱPrO)₁₂] ({Ti₈Cu₂}), and [Ti₁₀Co₂O₆(Dmg)₂(Pdc)₄(ⁱPrO)₁₈Cl₃] ({Ti₁₀Co₂}, DmgH₂ = dimethylglyoxime; PdcH₂ = pyridine-2,3-dicarboxylic acid) using dimethylglyoxime and different carboxylates as the synergistic ligands. By depositing the clusters {Ti₆Cu₂} and {Ti₁₀Co₂} on carbon cloth as electrodes, we investigated the electrocatalytic performance of TOCs for full water splitting for the first time. To reach a 10 mA cm^-2 current density in an alkaline solution, the {Ti₁₀Co₂}@CC electrode needs an overpotential as low as 120 and 400 mV for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. In addition, full water-splitting equipment with {Ti₁₀Co₂}@CC as a cathode and an anode need only 1.67 V to deliver a current density of 10 mA cm^-2. Our work confirmed the potential of noble metal-free TOCs as bifunctional cluster-based electrocatalysts for water splitting, and their activities can be tuned by doping with different metal ions.

Self-Assembly of Chiral Ferrocene-Functionalized Polyoxotitanium Clusters for Photocatalytic Selective Sulfide Oxidation

Here, we systematically studied the self-assembly behavior of chiral polyoxytitanium clusters for the first time. Through the cooperative assembly of ferrocenecarboxylic acid and ketoxime ligands, we successfully incorporated the planar chirality of ferrocene (Fc) into the layered {Ti₅} building blocks. The resulting {Ti₅Fc} clusters can be used as structural units to assemble into large ordered structures in various ways; either a pair of {Ti₅Fc} enantiomers are bridged by organic adhesive to form sandwich structures or two homochiral {Ti₅Fc} units participate in the assembly to form the large clusters. Depending on the assembly modes, the chirality of {Ti₅Fc} can be transferred to large nanoclusters or disappear to form mesostructures. The difference of the assembly modes between the {Ti₅Fc} units can also tune the photoelectric activity of the resulting clusters, which has been verified by using {Ti₁₀Fc-6/7} as catalysts for photocatalytic selective sulfide oxidation. This work not only is an important breakthrough in the study of the self-assembly of chiral nanoclusters but also provides an important reference for understanding of chiral transfer on the nanoscale.

Cd-Doped Polyoxotitanium Nanoclusters with a Modifiable Organic Shell for Photoelectrochemical Water Splitting

Incorporating heterometal and chromogenic groups into the titanium oxo cluster (TOC) nanomaterials is one of the effective strategies for the development of new high-performance photoelectrically active materials. In this Article, we report the structures and photoelectrochemical (PEC) performances of a family of TOCs, including pure [Ti₁₂O₈(OEt)₁₆L₈] ({Me-Ti₁₂}) and six Cd-doped clusters formulated as [H₄Cd₂Ti₁₀O₈(OEt)₁₆(L)₈(H₂O)₂] ({Cd₂Ti₁₀}; L = salicylic acid and their derivatives). The six Cd-doped clusters are isostructural, containing the same {Cd₂Ti₁₀O₈} core, but are protected by salicylic ligands modified with different functional groups. The compositions, structures, and solution stability of these clusters have been studied in detail by single-crystal X-ray diffraction and electrospray ionization mass spectrometry measurements. The embedding of heterometallic Cd(II) and chemical modification of organic protective shells can effectively regulate the PEC water oxidation activity of those clusters, with {F-Cd₂Ti₁₀} having the highest turnover number of 518.55 and the highest turnover frequency of 172.85 h^-1. Our work highlights the potential of using TOCs that do not contain noble metals as water oxidation catalysts, and their catalytic activity can be regulated by structural modification.

Protection of Ag Clusters by Metal-Oxo Modules

Monodisperse and atomically precise Ag nanoclusters have attracted considerable recent research interest. A conventional silver cluster usually consists of a silver metallic kernel and an organic peripheral ligand shell. Nevertheless, the present inevitable problem is the unsatisfied stability of such nanoclusters. In this concept, we will give an introduction to Ag clusters protected by metal-oxo modules which exhibit enhanced stability and unique properties. Accordingly, three different types of clusters are summarized: (1) Ag clusters protected by mononuclear oxometallates; (2) Ag clusters protected by block-like metal-oxo clusters; (3) Ag clusters protected by hollow-like metal-oxo clusters. The aim of this concept is to offer possible general guidance and insight into future rational design of more metal-oxo clusters protected silver clusters or even other coinage metal nanoclusters.