Bioinspired Polyoxo-titanium Cluster for Greatly Enhanced Solar-Driven CO2 Reduction.

Developing artificial enzymes with excellent catalytic activities and uncovering the structural and chemical determinants remain a grand challenge. Discrete titanium-oxo clusters with well-defined coordination environments at the atomic level can mimic the pivotal catalytic center of natural enzymes and optimize the charge-transfer kinetics. Herein, we report the precise structural tailoring of a self-assembled tetrahedral Ti4Mn3-cluster for photocatalytic CO2 reduction and realize the selective evolution of CO over specific sites. Experiments and theoretical simulation demonstrate that the high catalytic performance of the Ti4Mn3-cluster should be related to the synergy between active Mn sites and the surrounding functional microenvironment. The reduced energy barrier of the CO2 photoreduction reaction and moderate adsorption strength of CO* are beneficial for the high selective evolution of CO. This work provides a molecular scale accurate structural model to give insight into artificial enzyme for CO2 photoreduction.

Macrocyclic Inorganic Tin-Containing Oxo Clusters: Heterometallic Strategy for Configuration and Catalytic Activity Modulation.

In this work, the first examples of inorganic macrocyclic tin-oxo clusters which are stabilized by sulfate ligands are reported. As determined by X-ray diffraction and photoelectron spectroscopy analyses, the prepared inorganic Sn10 -oxo cluster displays interesting mixed valence behaviors, with 8 Sn4+ located at the cyclic skeleton and two Sn2+ encapsulated in the center. When further introducing Ti4+ and In3+ ions to the synthetic systems, heterometallic Sn2 Ti6 and SnIn5 Ti6 complexes with Ti6 (SO4 )9 and SnIn5 (SO4 )12 macrocyclic skeletons were prepared whose configuration and packing models were affected by the ionic radius of incorporated metals. Moreover, comparative CO2 reduction experiments confirm that such heterometallic composition can significantly improve the catalytic activities of these inorganic macrocyclic oxo clusters. This work represents a milestone in constructing inorganic tin complexes and also macrocyclic metal oxo clusters with tunable configurations and properties.

Ti4(embonate)6 Cage-Ligand Strategy on the Construction of Metal-Organic Frameworks with High Stability and Gas Sorption Properties.

Herein we report an efficient strategy to construct cage-based metal-organic frameworks (MOFs) via the assembly of Ti4L6 (L = embonate) cages and N-contained ligands with Mn2+ and Zn2+ ions, respectively, and two Ti4L6-cage-based MOFs (PTC-219 and PTC-220) with high stability and gas sorption properties have been generated through two-step reactions, respectively.

Embonic Acid Functionalized Niobium Complexes with Selective Dye Sorption Properties.

Presented here are binuclear Nb2, tetranuclear Ti2Nb2, and dodecanuclear Nb12 complexes decorated by embonic acid ligands. These structures feature a unique Ti-O-Nb or Nb-O-Nb subunit. Besides, the unprecedented dodecanuclear Nb12 cluster further displays a porous three-dimensional packing framework and stability in water, affording an interesting selective uptake for methylene blue molecules over rhodamine B.

Water-Soluble and Ultrastable Ti4L6 Tetrahedron with Coordination Assembly Function.

We have successfully constructed a tetrahedral Ti4L6 cage with calixarene-like coordination-active vertices. It further features high solubility and stability in H2O and DMF/H2O solution, affording an interesting stepwise assembly function with other metal ions. Through trapping of different amounts of Co or Ln ions, the Ti4L6 tetrahedra can be organized into various dimensional architectures, including a Ti4L6-Co3 cage, a Ti4L6-Ln2 cage, a Ti4L6-Ln2 chain, and a three-dimensional Ti4L6-Ln framework. An unusual mixed-valence phenomenon was observed in the Ti4L6 cage, whose Ti3+/4+ compositions were adequately identified by electron spin resonance and X-ray photoelectron spectroscopy analyses. More remarkably, the calixarene-like oxygen vertices of the Ti4L6 cage can also be used for the recognition of C3-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.

Polycatenation tuned microporosity of two metal-tris(4'-carboxybiphenyl)amine frameworks with multilayer structures.

By employing a nanosized tris(4'-carboxybiphenyl)amine ligand to assemble with Zn2+ ions, a novel trilayer network (FIR-37) and an unprecedented 2D → 3D microporous polycatenation framework (FIR-38) based on unusual tetralayers have been synthesized and structurally characterized. FIR-38 shows permanent porosity with a Langmuir surface area of 1408.4 m2 g-1.