Hailian Li

Design and synthesis of an exceptionally stable and highly porous metal-organic framework

Open metal–organic frameworks are widely regarded as promising materials for applications in catalysis, separation, gas storage and molecular recognition. Compared to conventionally used microporous inorganic materials such as zeolites, these organic structures have the potential for more flexible rational design, through control of the architecture and functionalization of the pores. So far, the inability of these open frameworks to support permanent porosity and to avoid collapsing in the absence of guest molecules, such as solvents, has hindered further progress in the field. Here we report the synthesis of a metal–organic framework which remains crystalline, as evidenced by X-ray single-crystal analyses, and stable when fully desolvated and when heated up to 300 °C. This synthesis is achieved by borrowing ideas from metal carboxylate cluster chemistry, where an organic dicarboxylate linker is used in a reaction that gives supertetrahedron clusters when capped with monocarboxylates. The rigid and divergent character of the added linker allows the articulation of the clusters into a three-dimensional framework resulting in a structure with higher apparent surface area and pore volume than most porous crystalline zeolites. This simple and potentially universal design strategy is currently being pursued in the synthesis of new phases and composites, and for gas-storage applications.

AN OPEN-FRAMEWORK GERMANATE WITH POLYCUBANE-LIKE TOPOLOGY

Body-centered Ge9 parallelepiped building blocks form the basis of the structure of [Ge9 O18 (OH)4 ]⋅2 (H2 ppz)⋅0.5 (H2 O) (ASU-14, ppz=piperazine). In this new structure type for an open-framework germanate (see picture for a section of the structure) the building blocks are linked together at each of their eight vertices to give the rare polycubane topology with an intersecting channel system of ten- and eight-membered rings (pore sizes 5×6 and 4×4 Å2 , respectively) in which the piperazinium cations and water molecules reside.

Design and synthesis of metal-carboxylate frameworks with permanent microporosity

Metal-carboxylate clusters are ideally suited as secondary building units (SBU) for the assembly of extended open frameworks. Examples extracted from the chemistry of the multidentate building block 1,4-benzenedicarboxylate (BDC) show that Zn(BDC) clusters lead to the formation of rigid, stable and truly microporous metal-carboxylate networks. Gas sorption isotherms measured for this class of materials show type (I) gas uptake that is analogous to those observed for zeolites and molecular sieves.

Construction of a new open-framework solid from1,3,5-cyclohexanetricarboxylate and zinc(II) building blocks

Addition copolymerization of cis,cis-1,3,5-cyclohexanetricarboxylate (CTC) with zinc(II) at 25 °C yielded the extended co-ordination solid, Zn 3 [(CTC)(C 5 H 5 N)] 2 · 2(CH 3 ) 2 NC(O)H, which has one-dimensional channels with an aperture of nearly 6 A as found by an X-ray crystallographic study.

Synthesis and Structure of a Metal-Organic Solid Having the Cadmium(II) Sulfate Net

Reaction of silver(I) nitrate and hexamethylenetetramine (HMTA) gives crystals of Ag2(HMTA)(N0 3)2, which was formulated by elemental microanalysis and a single crystal x-ray study. Its Ag2({MTA) open-framework is the first example of a decorated CdSO 4 net. The relative orientation of the tetrahedral HMTA building blocks in this structure point to numerous opportunities toward constructing novel chiral and polar porous frameworks.