We have successfully constructed a tetrahedral TiL cage with calixarene-like coordination-active vertices. It further features high solubility and stability in HO and DMF/HO solution, affording an interesting stepwise assembly function with other metal ions. Through trapping of different amounts of Co or Ln ions, the TiL tetrahedra can be organized into various dimensional architectures, including a TiL-Co cage, a TiL-Ln cage, a TiL-Ln chain, and a three-dimensional TiL-Ln framework. An unusual mixed-valence phenomenon was observed in the TiL cage, whose Ti compositions were adequately identified by electron spin resonance and X-ray photoelectron spectroscopy analyses. More remarkably, the calixarene-like oxygen vertices of the TiL cage can also be used for the recognition of C-symmetric dye molecules through N-H···O hydrogen bonding. Accordingly, driven by visible light, selective and efficient homogeneous photodecomposition of acid blue 93 and alkali blue 4B were successfully achieved. Therefore, this work not only represents a milestone in constructing symmetric Ti-based cages with interesting coordination assembly function but also provides a new method for preparing technologically important soluble photoactive cages.
Many metal–organic cages (MOCs) and a few hydrogen‐bonded organic cages (HOCs) have been investigated, but little is reported about cooperative self‐assembly of MOCs and HOCs. Herein, we describe an unprecedented MOC&HOC co‐crystal composed of tetrahedral Ti4L6 (L=embonate) cages and in‐situ‐generated [(NH3)4(TIPA)4] (TIPA=tris(4‐(1H‐1,2,4‐triazol‐1‐yl)phenyl)amine) cages. Chiral transfer is observed from the enantiopure Ti4L6 cage to enantiopure [(NH3)4(TIPA)4] cage. Two homochiral supramolecular frameworks with opposite handedness (PTC‐235(Δ) and PTC‐235(Λ)) are formed. Such MOC&HOC co‐crystal features high stability in water and other solvents, affording single‐crystal‐to‐single‐crystal transformation to trap CH3CN molecules and identify disordered NH4+ cations. A tablet pressing method is developed to test the third‐order nonlinear optical property of KBr‐based PTC‐235 thin film. Such a thin film exhibits an excellent optical limiting effect.
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