A pcu-type metal–organic framework based on covalently quadruple cross-linked supramolecular building blocks (SBBs): structure and adsorption properties† Chuanqiang Li, a Wenge Qiu, * a Wei Shi, b Haibin Song, b Guangmei Bai, a Hong He, * a Jian Li a and Michael J. Zaworotko c Received 18th October 2011, Accepted 31st December 2011 DOI: 10.1039/c2ce06384k A flexible ligand with two 1,3-benzenedicarboxylate units has been used to construct a microporous metal–organic framework with pcu topology based on supramolecular building blocks (SBBs). The obtained Cu(II) MOF exhibits a noticeable CO 2 adsorption hysteresis and a comparable methane adsorption capacity at room temperature. In recent years, design and synthesis of functional metal–organic materials (MOMs) based on the strategies of crystal engineering have attracted much attention due to their potential applications and fascinating structural diversities. 1 Remarkable progress has been made in this field, largely owing to efficient design strategies. 2 However, the preparation of MOMs with predictable structures is still a challenge since the self-assembly process of metal ions and organic ligands depends on many factors, including solvents, concentrations of metal ions and ligand precursor, pH value, temperature, etc. The use of metal–organic polyhedra (MOPs) as supramolecular building blocks (SBBs) for the construction of porous frameworks is a powerful strategy, because MOPs themselves have cavities and possess high symmetry, leading to the possibility of a crystal engineering strategy for MOMs fabrication with highly specific control over the topology. Successful examples include tetrahedra, 3 hexahedra (cubes), 4 octahedra, 5 cuboctahedra, 6 trun- cated cuboctahedra (small rhombihexahedron), 1e,7,8 and trigonal prism. 9 Among these MOPs reported, small rhombihexahedron possesses O h symmetry and consists of 12 square molecular building blocks (MBBs) that generate 8 triangular and 6 square open ‘‘windows’’(Fig. 1b). It was extensively studied by several groups 8,10 since the angle between its vertices is 120  corresponding exactly to the angle subtended by meta-substituted benzene rings. It has been demonstrated that flexible cross-linked bdc (benzene-1,3-dicarbox- ylate) ligands at the 5-position of the isophthalate moieties can link square windows or faces to generate 6-connected pcu (primitive cubic) nets, 8 whereas the rigid linear cross-linked bdc ligands can afford 3,24-coordinated rht nets if triangular metal clusters 1e or triangular organic moieties are utilized. 10 This communication focuses on the metal–organic polyhedra strategy and structural diversity by demonstrating how cross-linking of Cu 2 (O 2 CR) 4 paddlewheels with Fig. 1 (a) Square shaped SBU constructed with two copper ions and four isophthalate moieties from different ligand molecules; (b) small rhombihexahedron supramolecular building block (SBB) generated via vertex linking of square MBBs; (c) crystal structure and schematic representation of 1 from the assembly of SBBs. a Department of Chemical Science and Engineering, College of environmental and energy engineering, Beijing University of Technology, Beijing, 100124, China. E-mail: qiuwenge@bjut.edu.cn; Fax: +86 10- 67391983; Tel: +86 10-67396588 b College of Chemistry, Nankai University, Tianjin, 300071, China. Tel: +86 22-23500305 c Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, CHE205 Tampa, Florida, USA. E-mail: xtal@usf.edu; Tel: +1 813-974-3451 † Electronic supplementary information (ESI) available. CCDC reference numbers 842117. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2ce06384k This journal is ª The Royal Society of Chemistry 2012 CrystEngComm Dynamic Article Links C < CrystEngComm Cite this: DOI: 10.1039/c2ce06384k www.rsc.org/crystengcomm COMMUNICATION Downloaded on 04 February 2012 Published on 26 January 2012 on http://pubs.rsc.org | doi:10.1039/C2CE06384K View Online / Journal Homepage