The development of organometal-oxo molecular cages remains challenging due to the difficulties associated with constructing novel structures through conventional bottom-up self-assembly methods. In this study, we present a rationally designed approach to construct the first family of novel fortress-like alkyl-Sn₁₂ molecular cages with size of ~ 0.8 × 0.7 nm. Utilizing an open hollow framework as a structural model, we employed a ligand regulation strategy to modify the skeleton and successfully create closed alkyltin-oxo molecular cages. Unlike previously reported football-shaped cages that solely feature alkyl or phenyl groups, our fortress-like alkyl-Sn₁₂ molecular cages are functionalized with various targeted π-conjugated bifunctional O/N ligands. This tunable functionalization allows us to explore the relationship between structure and nonlinear optical limiting (OL) properties at the nanoscale. The OL properties of these cages are influenced by the electron-donating or -withdrawing abilities of the ligands and the distance between adjacent cages (d(cages)). Additionally, the heavy atom substitution effect plays a significant role in the nonlinear OL response. Notably, the CTGU-SnC-9 cage exhibits the best nonlinear OL performance, attributed to its electron-donating groups and the large d(cages) value, outperforming both reported tin-oxo clusters and many other metal-oxo clusters/cages. This work provides new insights into the innovative construction and modulation of optical properties in organometal-oxo molecular cages.

Tin–oxo clusters have attracted considerable attention because they provide a platform for studying the structure–property relationship of tin oxide materials at the molecular level. Although different types of tin–oxo clusters have been developed, extended tin–oxo cluster-based structures and their corresponding discrete clusters are rarely obtained. In this study, we regulate reaction pathways to hierarchically assemble a novel discrete Sn₈–oxo cluster and its extended structure using a solvent strategy. The discrete Sn₈–oxo cluster (CTGU-SnC-1) is obtained because its coordination active sites are occupied by the esterifiable methanol in the solvent. The resulting one-dimensional chain (CTGU-SnC-2) is formed because of the coordination-driven assembly of active sites in the Sn₈ cluster without methanol in the solvent. In addition to single-crystal X-ray diffraction, these compounds were further characterized using powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, elemental analysis, and ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy. In addition, their electrocatalytic CO₂ reduction properties were explored. The extended structure CTGU-SnC-2 exhibits better electrocatalytic activity than the discrete cluster in the CO₂ reduction reaction.

Exploring a novel strategy for large-scale production of battery-type Ni(OH)₂-based composites, with excellent capacitive performance, is still greatly challenging. Herein, we developed a facile and cost-effective strategy to in situ grow a layer of Ni(OH)₂/Ti₃C₂T_x composite on the nickel foam (NF) collector, where Ti₃C₂T_x is not only a conductive component, but also a catalyst that accelerates the oxidation of NF to Ni(OH)₂. Detailed analysis reveals that the crystallinity, morphology, and electronic structure of the integrated electrode can be tuned via the electrochemical activation, which is beneficial for improving electrical conductivity and redox activity. As expected, the integrated electrode shows a specific capacity of 1.09 C cm⁻² at 1 mA cm⁻² after three custom activation cycles and maintains 92.4% of the initial capacity after 1500 cycles. Moreover, a hybrid supercapacitor composed of Ni(OH)₂/Ti₃C₂T_x/NF cathode and activated carbon anode provides an energy density of 0.1 mWh cm⁻² at a power density of 0.97 mW cm⁻², and excellent cycling stability with about 110% capacity retention rate after 5000 cycles. This work would afford an economical and convenient method to steer commercial Ni foam into advanced Ni(OH)₂-based composite materials as binder-free electrodes for hybrid supercapacitors.