Water-Soluble and Ultrastable Ti₄L₆ Tetrahedron with Coordination Assembly Function

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Coordination Chemistry

Background:

• Construction of discrete, soluble metal-organic cages remains a challenge.
• Developing functional cages with tunable assembly properties is of significant interest.

Purpose of the Study:

• To synthesize a novel tetrahedral titanium cage (Ti4L6) with calixarene-like vertices.
• To explore its stepwise assembly with metal ions and its potential applications in catalysis and recognition.

Main Methods:

• Synthesis and characterization of the Ti4L6 cage.
• Stepwise assembly with Cobalt (Co) and Lanthanide (Ln) ions.
• Analysis of mixed-valence states using Electron Spin Resonance (ESR) and X-ray Photoelectron Spectroscopy (XPS).
• Investigation of dye molecule recognition and photocatalytic degradation.

Main Results:

• Successfully constructed a highly soluble and stable tetrahedral Ti4L6 cage.
• Demonstrated stepwise assembly into various dimensional architectures (cages, chains, frameworks) by trapping Co or Ln ions.
• Observed and characterized a mixed-valence Ti3+/4+ phenomenon within the cage.
• Achieved selective and efficient visible-light-driven photodecomposition of dyes (Acid Blue 93, Alkali Blue 4B) via hydrogen bonding interactions.

Conclusions:

• The Ti4L6 cage represents a milestone in constructing symmetric, soluble, and functional Ti-based cages.
• The cage exhibits versatile coordination assembly and photoactivity, providing a new route for preparing advanced photoactive materials.