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Controlling the In situ Decomposition of Chain-Type Polyamines To Direct the Crystal Growth of Cobalt−zinc Phosphates

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posted on 02.07.2008, 00:00 by Ailing Lu, Niu Li, Yanfeng Ma, Haibin Song, Daiping Li, Naijia Guan, Honggen Wang, Shouhe Xiang
The in situ decomposition of tetraethylene-pentamine, triethylenetetramine, or diethylenetriamine has been controlled to direct the synthesis of three open-framework cobalt−zinc phosphates, CoZnPO4-I, CoZnPO4-II, and CoZnPO4-III. These phosphates can be synthesized as the intergrowth from a single gel at 200 °C in the presence of diethylenetriamine with propylamine as the assistant organic additive. Structure analysis reveals that species encapsulated in the structures of CoZnPO4-I, CoZnPO4-II, and CoZnPO4-III are ammonium, ethylenediaminum, and diethylenetriaminum, respectively, which can be attributed to the in situ decomposition of diethylenetriamine molecules during the crystallization procedure. It has been found that the presence of second organic amine redound to controlling the decomposition of these linear polyamines, such as diethylenetriamine, to form these three CoZnPO4 materials from a single gel. Pure phase of CoZnPO4-I, CoZnPO4-II, and CoZnPO4-III have also been obtained by varying assistant amines, crystallizing at a lower temperature, or using other linear polyamines, such as triethylenetetramine or tetraethylene-pentamine instead of diethylenetriamine as the main organic additives. Single-crystal X-ray diffraction analysis has shown that CoZnPO4-I is a novel metal phosphate. It crystallizes in hexagonal space group p6 3 (No.173), with a = 10.7207(5) Å, c = 8.7241(8) Å, V = 868.36(10) Å3, and Z = 4. Its three-dimensional framework can be considered as the stacking of six-ring sheet with the combination of UDUDUD (U, upward; D, downward) and UUUDDD linkages in the proportion 1:3. Its negative framework is charge-compensated by NH4 + cations, which are encapsulated in 694 cage of the structure. CoZnPO4-II crystallizes in the tetragonal system, space group P42 bc (No. 106), with a = b = 14.694(2) Å, c = 8.936(2) Å, V = 1929.4(6) Å3, and Z = 8, possesses DFT topology, and is built of ZnO4 (or CoO4), and PO4 tetrahedra with ethylenediaminum cation resided in the 8-member ring channels to compensate the negative framework charge. The three-dimensional architecture of CoZnPO4-III crystallizes in the trigonal system, space group (No. 148), with a = 13.5393(8) Å, c = 15.0443(10) Å, γ = 120°, V = 2388.3(3) Å3, and Z = 3, is built up of ZnO4(or CoO4), PO4 tetrahedra, and CoO6 octahedra with diethylenetriaminums encapsulated in the channels.