Metalorganic frameworks as precursor for metal oxide nanostructures Part I: MOFderived copper oxide embedded in carbon matrix

Three isostructural metalorganic framework materials (MOFs) formulated as M[(HBTC)(H2O)]ˑH2O(M = Cu for 1, Zn for 2 and Ca for 3) constructed with 1, 3, 5benzenetricarboxylate (BTC) were synthesised under hydro/solvothermal conditions. The three compounds were characterised on the basis of infrared and UVVis spectroscopy and the structure of 3 elucidated with the help of singlecrystal xray crystallography. The UVVis spectrum of 1 exhibited a unique band at 511 nm. In the region 520 – 534 nm, the band splits into two moderately intense peaks at 527 and 531 nm. These absorption peaks along with other bands at 629 and 638 nm were assigned to dd transitions of the copper (II) ion with distorted square planar geometry. The infrared spectra of the three compounds revealed that the ligand, BTC anion coordinated in a chelating and / or bridging mode to the metal center. The presence of absorption bands at 1699 cm1 in 1 and 2, (1681 cm1 in 3) can be attributed to protonated HBTC for 13. Singlecrystal Xray crystallographic studies of compound 3 revealed wellordered structure with BTC ligand linking the individual chains to form a network structure. On heating Cu(HBTC)(H2O)ˑH2O up to 400oC, a copperoxide embedded in carbon matrix was obtained with uniform particles of 10 100 nm size.