The long-standing challenge of designing and constructing new crystalline solid-state materials from molecular building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: we call this approach reticular synthesis. This chemistry has yielded materials designed to have predetermined structures, compositions and properties. In particular, highly porous frameworks held together by strong metal-oxygen-carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.

/pdf/reticular-synthesis-and-the-design-of-new-materials-lazbx7tdux.pdf

Reticular synthesis and the design of new materials

A strategy based on reticulating metal ions and organic carboxylate links into extended networks has been advanced to a point that allowed the design of porous structures in which pore size and functionality could be varied systematically. Metal-organic framework (MOF-5), a prototype of a new class of porous materials and one that is constructed from octahedral Zn-O-C clusters and benzene links, was used to demonstrate that its three-dimensional porous system can be functionalized with the organic groups –Br, –NH2, –OC3H7, –OC5H11, –C2H4, and –C4H4 and that its pore size can be expanded with the long molecular struts biphenyl, tetrahydropyrene, pyrene, and terphenyl. We synthesized an isoreticular series (one that has the same framework topology) of 16 highly crystalline materials whose open space represented up to 91.1% of the crystal volume, as well as homogeneous periodic pores that can be incrementally varied from 3.8 to 28.8 angstroms. One member of this series exhibited a high capacity for methane storage (240 cubic centimeters at standard temperature and pressure per gram at 36 atmospheres and ambient temperature), and others the lowest densities (0.41 to 0.21 gram per cubic centimeter) for a crystalline material at room temperature.

http://science.sciencemag.org/content/sci/295/5554/469.full.pdf

Systematic Design of Pore Size and Functionality in Isoreticular MOFs and Their Application in Methane Storage

From molecules to crystal engineering: supramolecular isomerism and polymorphism in network solids.

Kenji Sumida, David L. Rogow, Jarad A. Mason, Thomas M. McDonald, Eric D. Bloch, Zoey R. Herm, Tae-Hyun Bae, Jeffrey R. Long

Carbon Dioxide Capture in Metal–Organic Frameworks

Secondary building units (SBUs) are molecular complexes and cluster entities in which ligand coordination modes and metal coordination environments can be utilized in the transformation of these fragments into extended porous networks using polytopic linkers (1,4-benzenedicarboxylate, 1,3,5,7-adamantanetetracarboxylate, etc.). Consideration of the geometric and chemical attributes of the SBUs and linkers leads to prediction of the framework topology, and in turn to the design and synthesis of a new class of porous materials with robust structures and high porosity.

/pdf/modular-chemistry-secondary-building-units-as-a-basis-for-1s30wd1erl.pdf

Modular chemistry: secondary building units as a basis for the design of highly porous and robust metal-organic carboxylate frameworks.

Gas sorption isotherm measurements performed on the evacuated derivatives of four porous metal−organic frameworks (MOF-n), Zn(BDC)·(DMF)(H2O) (DMF = N,N‘-dimethylformamide, BDC = 1,4-benzenedicarboxylate) (MOF-2), Zn3(BDC)3·6CH3OH (MOF-3), Zn2(BTC)NO3·(C2H5OH)5H2O (BTC = 1,3,5-benzenetricarboxylate) (MOF-4), and Zn4O(BDC)3·(DMF)8C6H5Cl (MOF-5), reveal type I isotherms for n = 2, 3, and 5, which is evidence of microporous and accessible channels having high structural integrity and organization. Although gas sorption into MOF-4 was not observed, careful examination of its ethanol sorption isotherms at 22 and 32 °C point to the presence of coordinatively unsaturated zinc centers within its pores, which upon ethanol sorption undergo coordination transitions from 3- to 4-, 4- to 5-, and 5- to 6-coordination. MOF-n materials were produced by building the extended analogues of molecular metal carboxylate clustersa strategy that has allowed the realization of the most porous and thermally stable framework yet re...

and Hailian Li

Papers

Highly Porous and Stable Metal−Organic Frameworks: Structure Design and Sorption Properties