| In recent decades, metal-organic frameworks (MOFs) have attracted great interest of chemists, not only because of their modulation and diversity of structures, also their extensive promising application such as gas absorption, ion exchange, catalysis, magnetic properties and optical properties. Ion exchange is particularly intriguing, due to its company with structural changes, which play an important role in the properties modulation, further contribute greatly to the exploiting and application of new materials.Firstly, under 80℃hydrothermal condition, we synthesized blue crystals of {[Cu6(TTTMB)8(OH)4(H20)6]-8(NO3)·34.5H20}n (1) with a rare reported Schlafli symbol of 83·86·-86.There are numerous nitrate in the framework of 1 and 1 is insoluble in KI solution, which are essential to investigate a SC-SC transformation process upon anion exchange. After 5h suspending in KI aqueous solution,1 turned into blue black. X-ray analysis shows the blue black crystals of {[Cu6(TTTMB)8l3]·9I·26H2O}n(2). Comparing with 1,2 have different coordination numbers, as well as the formation of Cu2+…I- interaction. XPS of 2 demonstrates that coppers are in Cu2+ state. AFM proves that the process of 1 to 2 is a single crystal to single crystal transformation. The PXRD pattern of 2 is slightly different from that of 1, showing the structural transformation. From the X-ray fluorescence (XRF) and energy dispersive X-ray spectroscopy (EDS) spectrum, we can confirm that there is high concentration of iodine, which means I- enter the framework of 2. The IR spectroscopy of 2 shows the intense peak NO3- disappears. Interestingly,2 can transform to 1',1 and 1'have the same structure, which is a reversible single crystal to single crystal transformation. The study of postsynthetic modulation of 1 and 2 shows no obvious change of magnetic behavior and the catalysis investigation shows that the catalysis activity of 1 is much higher than that of 2. The anion exchange might be regarded as a promising and powerful method to modulate structures and properties of crystalline materials.Secondly, under hydrothermal condition, we obtained a light yellow polymer [Zn2(SO4)(L)2(H2O)4] H2BTEC·3H2O (3) with two dimensional channels. Putting crystals 3 into Cu(NO3)2 aqueous solution for a month, we gained blue single crystals of [Cu2(TTTMB)2BTEC(μ-H20)(H2O)4]·7H20 (4), which is a three dimensional net. This is an infinite recurrent dissolving-exchange-crystallization crystals transformation process, as well as a solvent-mediated cation-exchange in structural transformation from 2D channels to 3D nets. In addition, we obtained polymer [Cu3 (TTTMB)2(H2BTEC)3(H2O)3]·3H2O (5) through direct method which is different from the structure of 4. Meanwhile, [Cd2(SO4)(TTTMB)2(H2O)4] H2BTEC·3H2O (6), the isostucture of 3, has the same function with 3.Thirdly, three coordination polymers by different metal ions, TTTMB and pyridine-2,6-dicarboxylic acid (DPC) were synthesized under hydrothermal condition, [Cd(TTTMB) (DPC) (H2O)2]·2H2O (7), a two dimensional structure linked by hydrogen bonds; nanostructural [Zn (TTTMB) (H2O)2] [Zn (DPC)2]-5H2O (8)å'Œ[Cu (TTTMB) (H2O)2] [Cu (DPC)2]·5H2O (9). |
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