Shou-Tian Zheng

Pore Space Partition and Charge Separation in Cage-within-Cage Indium−Organic Frameworks with High CO2 Uptake

The integration of negatively charged single-metal building blocks {In(CO2)4} and positively charged trimeric clusters {In3O} leads to three unique cage-within-cage-based porous materials, which exhibit not only high hydrothermal, thermal, and photochemical stability but also attractive structural features contributing to a very high CO2 uptake capacity of up to 119.8 L/L at 273 K and 1 atm.

Cubic Polyoxometalate−Organic Molecular Cage

Tris(hydroxymethyl)aminomethane (Tris) was successfully grafted onto the surface of a Ni(6)-substituted polyoxotungstate formed in situ to further generate a three-connected polyoxometalate building block. The cooperative assembly of Tris functionalized three-connected building blocks and rigid 1,3,5-benzenetricarboxylate gave rise to an unprecedented cubic polyoxometalate-organic molecular cage with high thermal and hydrothermal stability.

Selective anion exchange with nanogated isoreticular positive metal-organic frameworks

Crystalline porous materials, especially inorganic porous solids such as zeolites, usually have negative frameworks with extra-framework mobile cations and are widely used for cation exchange. It is highly desirable to develop new materials with positive frameworks for selective anion exchange and separation or storage and delivery. Recent advances in metal-organic framework synthesis have created new opportunities in this direction. Here we report the synthesis of a series of positive indium metal-organic frameworks and their utilization as a platform for the anion exchange-based separation process. This process is capable of size- or charge-selective ion-exchange of organic dyes and may form the basis for size-selective ion chromatography. Ion-exchange dynamics of a series of organic dyes and their selective encapsulation and release are also studied, highlighting the advantages of metal-organic framework compositions for designing host materials tailored for applications in anion separation and purification.

Development of Composite Inorganic Building Blocks for MOFs

A general direction for diversifying metal-organic frameworks (MOFs) is demonstrated by the synthesis of composite inorganic clusters between indium and s-, d-, and f-block elements. These previously unknown heterometallic clusters, with various nuclearity, geometry, charge, and metal-to-metal ratios, significantly expand the pool of inorganic building blocks that are highly effective for the construction of porous MOFs with high gas uptake capacity.

Urothermal Synthesis of Crystalline Porous Materials

Pores from Urea Urea derivatives are shown here to be a highly verstaile solvent system for the synthesis of crystalline solids. In particular, reversible binding of urea derivatives to framework metal sites has been utilized to create a variety of materials integrating both porosity and open-metal sites.

Single-Walled Polytetrazolate Metal–Organic Channels with High Density of Open Nitrogen-Donor Sites and Gas Uptake

The self-assembly between zinc dimer and 1,3,5-tris(2H-tetrazol-5-yl)benzene (H(3)BTT), promoted by a urea derivative, leads to a highly porous 3D framework with a large percentage (67%) of N-donor sites unused for bonding with metals. The material exhibits high gas storage capacity (ca. 1.89 wt % H(2) at 77 K and 1 atm; 98 cm(3)/g CO(2) at 273 K and 1 atm), even in the absence of open metal sites. The high percentage of open N-donor sites, coupled with the low framework density resulting from single-walled channels, is believed to contribute to the high uptake capacity.

Synthesis and Photocatalytic Properties of a New Heteropolyoxoniobate Compound: K10[Nb2O2(H2O)2][SiNb12O40]·12H2O

The synthesis and photocatalytic properties of a heteropolyoxoniobate, K(10)[Nb(2)O(2)(H(2)O)(2)][SiNb(12)O(40)]·12H(2)O (1), are reported, revealing an important role of Zr(4+) additives in the crystallization. Compound 1 exhibits overall photocatalytic water splitting activity, and its photocatalytic activity is significantly higher than that of Na(10)[Nb(2)O(2)][SiNb(12)O(40)]·xH(2)O (2). Fluorescence lifetime measurements suggest that the enhanced photocatalytic activity of 1 likely results from a larger yield of longer-lived charge trapping states in 1 due to the coordination of one water molecule to the bridging Nb(5+), leading to highly unsymmetrical seven-coordinated Nb(5+) sites.

Mimicking Zeolite to Its Core: Porous Sodalite Cages as Hangers for Pendant Trimeric M3(OH) Clusters (M = Mg, Mn, Co, Ni, Cd)

A new class of zeolite-type porous materials in which 3D frameworks are covalently functionalized with crystallographically ordered pendant metal clusters have been synthesized. This work demonstrates a new paradigm for and the feasibility of functionalizing zeolite-type frameworks through the conversion of extraframework sites in mineral zeolites into part of the framework for occupation by dangling metal clusters in metal-organic frameworks.

Aluminoborates with Open Frameworks: Syntheses, Structures, and Properties

Five aluminoborates Al[B(5)O(10)] x H(2)dab x 2 H(2)O (1), [Al(B(4)O(9))(BO)] x H(2)en (2), [Al(B(4)O(9))(BO)] x H(2)dap (3), K(2)Al[B(5)O(10)] x 4 H(2)O (4), and (NH(4))(2)Al[B(5)O(10)] x 4 H(2)O (5) have been synthesized under hydrothermal conditions and characterized by means of elemental analysis, IR, TG analysis, MAS NMR, UV-vis and fluorescence spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction, and NLO determination. The structure 1 comprises of AlO(4) tetrahedra and B(5)O(10) clusters and contains 12-, 11-, and 8-MR 3D-intersecting channels with a CrB(4) topological net. Structures 2 and 3 are both constructed from the same AlB(5)O(13) clusters and exhibit a six-connected framework with 4(12)6(3) topology. Structures 4 and 5 are isomorphous and are composed of AlO(4) tetrahedra and B(5)O(10) clusters that possess odd 11-MR channels and 8-MR helical channels. Structures 2-5 crystallized in an acentric structure and presented good SHG properties. UV-vis spectral investigation indicates that they are wide-band-gap semiconductors. The electronic structure calculations for the compounds also have been performed.

Entrapment of Metal Clusters in Metal–Organic Framework Channels by Extended Hooks Anchored at Open Metal Sites

Reported here are the new concept of utilizing open metal sites (OMSs) for architectural pore design and its practical implementation. Specifically, it is shown here that OMSs can be used to run extended hooks (isonicotinates in this work) from the framework walls to the channel centers to effect the capture of single metal ions or clusters, with the concurrent partitioning of the large channel spaces into multiple domains, alteration of the host-guest charge relationship and associated guest-exchange properties, and transfer of OMSs from the walls to the channel centers. The concept of the extended hook, demonstrated here in the multicomponent dual-metal and dual-ligand system, should be generally applicable to a range of framework types.