Hydrothermal synthesis and characteristics of 3-D hydrated bismuth oxalate coordination polymers with open-channel structure

Two new 3-D porous bismuth coordination polymers, (C5NH6)2[Bi2(H2O)2(C2O4)4]·2H2O 1 and (NH4)[Bi(C2O4)2]·3H2O 2, have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the monoclinic symmetry, P21/c space group with a=10.378(2) Å, b=17.285(3) Å, c=16.563(5) Å, α=90°, β=119.66(2)°, γ=90°, V=2581.8(10) Å3, Z=4, R1=0.0355 and wR2=0.0658 for unique 4713 reflections I >2σ(I). Compound 2 crystallizes in the tetragonal symmetry, I41/amd space group with a=11.7026(17) Å, b=11.7026(17) Å, c=9.2233(18) Å, α=90°, β=90°, γ=90°, V=1263.1(4) Å3, Z=32, R1=0.0208 and wR2=0.0518 for unique 359 reflections I> 2σ(I). Compounds 1 and 2 are 3-D open-framework structures with a 66 uniform net, which consist of honeycomb-like layers connected to each other by oxalate units. While different guest molecules fill in their cavities of honeycomb-like layers, study of ultrasonic treatment on 2 indicates the replacement of NH4+ by K+ on potassium ion exchange. Thermogravimetric analysis indicates that the open-channel frameworks are thermally stable up to 200 °C, and other characterizations are also described by elemental analysis, IR and ultraviolet–visible diffuse reflectionintegral spectrum (UV–Vis DRIS).