Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (19): 2012-2015.DOI: 10.6023/A12080546 Previous Articles     Next Articles



林祖金, 林熙, 曹荣   

  1. 中国科学院福建物质结构研究所 结构化学国家重点实验室 福州 350002
  • 投稿日期:2012-08-12 发布日期:2012-09-24
  • 通讯作者: 曹荣
  • 基金资助:

    项目受国家重点基础研究发展计划(973计划, Nos. 2011CB932504, 2012CB821705);国家自然科学基金(Nos. 91022007, 21003128和20901078);福建省纳米材料重点实验室(No. 2006L2005)和中国科学院重要方向性课题的资助.

Construction of Two Octahedral Cage-based Metal-organic Frameworks

Lin Zujin, Lin Xi, Cao Rong   

  1. State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002
  • Received:2012-08-12 Published:2012-09-24
  • Supported by:

    Project supported by the 973 Program (Nos. 2011CB932504, 2012CB821705), National Natural Science Foundation of China (Nos. 91022007, 21003128, and 20901078), Fujian Key Laboratory of Nanomaterials (No. 2006L2005), and Key Projects from CAS.

Two isostructural octahedral metal-organic frameworks formulated as {[Zn3TBTC2(DMA)(H2O)]·3DMA·3H2O}n (1), {[Cd3TBTC2(DMA)2(H2O)2]·2DMA·2H2O}n (2) have been successfully prepared via solvothermal synthesis based on a predesigned semi-rigid ligand, 1,3,5-tris[3-(carboxyphenyl)oxamethyl]-2,4,6-trimethylbenzene acid (H3TBTC). In the structure, the semi-rigid ligand adopts cis,cis,cis- and cis,trans,trans-conformations. Six cis,cis,cis- conformational TBTC3- ligands connect six M3(COO)6 (M=Zn(II) or Cd(II) secondary building units (SBUs) to form a pumpkin-shaped metal- organic nanocage. Viewing only the SBUs as vertexes, the pumpkin-shaped nanocage can be seen as a slightly distorted octahedral nanocage. Acting as supramolecular building blocks (SBBs), every octahedral nanocage connects 18 cis,trans,trans-conformational TBTC3- ligands, while every cis,trans,trans-conformational TBTC3- ligand connects three octahedral cages. Thus, the framework can be simplified as a (3,18)-connected network with point symbol of {433.684.836}{43}6. Moreover, upon removal of free guest solvent molecules, compounds 12 have metal clusters locating in the tunnel walls, which may have strong interaction with molecules with high quadrapole moment, and they show preferential adsorption of CO2 over N2/H2. The resulting materials have potential for separation of CO2 from other gas molecules such as N2 and H2. The solid state photoluminescent spectra of 12 as well as the free H3TBTC ligand were examined at room temperature. When excited at 320 nm, the free ligand shows a maximum emission at 434 nm, which can be ascribed to the π-π* transition of the aromatic rings. The strongest emission peak for compounds 12 are observed at about 424 nm. By comparison of the emission energies and profiles of the free H3TBTC ligand and compounds 12, the luminescent behavior of compounds 12 are considered to be originated from H3TBTC ligands. The blue-shifted bands of their emissions may result from the fact that the ligands are not allowed to relax along the torsional mode upon photoexcitation.

Key words: metal-organic frameworks, coordination polymers, nanocage, semi-rigid ligand, gas adsorption, luminescence