Crystal Engineering DOI: 10.1002/anie.201104688 Network Diversity through Decoration of Trigonal-Prismatic Nodes: Two-Step Crystal Engineering of Cationic Metal–Organic Materials** Alexander Schoedel, Lukasz Wojtas, StephenP. Kelley, Robin D. Rogers, Mohamed Eddaoudi, and Michael J. Zaworotko* During the past decade porous metal–organic material (MOM) networks constructed from metal-based nodes (metal ions or metal clusters) and bridging organic ligand (linkers) have attracted ever increasing scientific interest. [1] Their modular nature imparts structural and compositional diversity, tunable functionality, and multiple properties within a single material. In particular, that MOMs can exhibit extra- large surface area means that they represent a uniquely promising class of materials to solve technological challenges related to gas storage and separation, environmental reme- diation, catalysis, sensing, and drug delivery. Crystal engineer- ing [2] played a major role in the early development of MOMs as exemplified by the high symmetry nets that can be generated by linking polygonal or polyhedral nodes such as tetrahedra (dia), [3] octahedra (pcu), [3c] squares (nbo), [3c, 4] and trigonal prisms (acs). [5] The aforementioned nets might be described as platforms because they are fine-tunable in terms of both scale and properties as there are many nodes and linkers that can sustain these structures. Pyridyl linkers such as 4,4’-bipyridine were initially exploited in such a capacity [6] but the majority of extra-large surface area MOMs are based upon carboxylate linkers such as benzene-1,3-dicarboxylic acid (1,3-BDC), [7] benzene-1,4-dicarboxylic acid (1,4-BDC), [8] and benzene-1,3,5-tricarboxylic acid (BTC). [9] Such linkers complement synthetically accessible and highly symmetrical metal carboxylate nodes such as [Cu 2 (CO 2 ) 4 ], [Zn 4 (m 4 -O)- (CO 2 ) 6 ] and [{M 3 (m 3 -O)(CO 2 )} 6 ] (M = Cr, Fe). The exploita- tion of [Cu 2 (CO 2 ) 4 ] , the “square paddlewheel”, has proven to be particularly fruitful since ligand design [10] or the use of mixed ligands [11] facilitates a plethora of highly porous polyhedral nets. [{M 3 (m 3 -O)(CO 2 )} 6 ], the “trigonal prism”, has also afforded highly porous materials, as exemplified by MIL-100 [12] and MIL-101. [13] However, even though this node is remarkably robust, [14] its structures tend to form only microcrystalline materials and require harsh synthetic con- ditions. We describe herein a crystal engineering strategy that exploits preformed molecular building blocks (MBBs) based upon water-stable trigonal prisms that are decorated with pyridyl moieties. A two-step modular approach that opens up a broad new class of bimetallic MOMs is thereby facilitated. Two-step processes to form heterobimetallic frameworks are known [15] and are based on the synthesis of a metal complex that is subsequently connected to a different metal ion. To the best of our knowledge, high-connectivity metal complexes that afford high symmetry nets with extra-large channels have not yet been studied in this context. Our two- step process involves isolation of a trigonal prism decorated by pyridyl moieties and then coordinating this highly soluble trigonal-prismatic Primary Molecular Building Block (tp- PMBB-1) to different metals through its six exodentate pyridyl moieties (Scheme 1). We coin the term PMMB to draw analogies to the primary building unit (PBU) in zeolite chemistry. In this context the different connections of PMBBs to various Secondary Molecular Building Blocks (SMBBs) lead to the structural diversity. This approach enables us to exploit both metal–carboxylate and metal–pyridyl bonds and ensures that the nets thereby generated will be positively charged. The first three examples of such nets, tp-PMBB-1- snx-1, -snw-1, and -stp-1 (nomenclature describes both the primary building block and the topology of the resulting net) are described herein. The building block tp-PMBB-1 [Cr 3 (m 3 -O)(isonic) 6 ] + (isonic = pyridine-4-carboxylate) [16] represents a discrete and robust “hexapyridyl” 6-connected node that is well-suited for the subsequent synthesis of a plethora of networks with nanoscale features. Its coordination chemistry with two metals is detailed herein: a linear but bendable linker (Ag + ) and a rigid square-planar metal node (Cd 2+ ). Our results demonstrate the ability of Ag + to exist in nonlinear geometry and facilitate two new network topologies for trigonal- prismatic nodes, snx (six-connected net type x) (6,6) and snw (six-connected net type w) (6,6), rather than the default acs net. [5] A cationic net with acs topology formed by another tp-PMBB can also be formed and will be reported elsewhere. For the rigid CdN 4 node we anticipated stp (square trigonal prism) (6,4) topology [17] consisting of a trigonal-prismatic and a rectangular-vertex figure, and the first nanoporous variant of this net was indeed isolated. [*] A. Schoedel, Dr. L. Wojtas, Prof. Dr. M. J. Zaworotko Department of Chemistry, University of South Florida 4202 East Fowler Ave., SCA400, Tampa, FL 33620 (USA) E-mail: xtal@usf.edu Homepage: http://chemistry.usf.edu/faculty/zaworotko/ S. P. Kelley, Prof. Dr. R. D. Rogers Department of Chemistry Box 870336, The University of Alabama Tuscaloosa 3006D Shelby Hall, 250 Hackberry Lane Tuscaloosa, AL 35487 (USA) Prof. Dr. M. Eddaoudi Chemical Science, King Abdullah University of Science and Technology Thuwal 23955-6900 (Kingdom of Saudi Arabia) [**] This work is supported by Award No. FIC/2010/06, made by the King Abdullah University of Science and Technology (KAUST). We thank Dr. T.T. Ong and Dr. J.A. Perman for the help in sample characterization and S. Elsaidi for fruitful discussions. Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/anie.201104688. 11421 Angew. Chem. Int. Ed. 2011, 50, 11421 –11424  2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim