论文部分内容阅读
Ionothermal syntheses,using ionic liquids or eutectic mixtures to serve as both the solvent and the structure directing agent,have some interesting features and advantages over the conventional approach to preparing crystalline porous materials.[1] Herein,we synthesized a novel open-framework zirconium phosphate from an eutectic mixture,|(C2H7NH)8(H2O)8|[Zr32P48O176F8(OH)16] (denoted as ZrPOF-EA).[2] Its structure is a complicated one,consisting of [41482] units arranged in a rectangular array connected via ZrO6,ZrO5F and PO4 linkages (Figure 1).There are 3-,4-,5-,6-,7- and 8-ring units in the structure,and these form small 1-dimensional channels parallel to the c- (7-ring) and a- (8-ring) axes.There are terminal hydroxyl groups and these block the 8-ring channels that would otherwise intersect the 7-ring channels to form a two-dimensional channel system.The guest molecules occupying the channels be removed by calcination without causing the collapse of the host framework.The surface area was calculated from CO2 adsorption experiments and found to be 166 m2 g-1.In ZrPOF-EA,the oval 7- and 8-ring windows have dimensions of ca.4.0 ? x 3.0? and 3.9 ? x 3.2 ? respectively.Adsorption experiments (Figure 2) shows that the adsorption capacity for CO2 is markedly higher than that for CH4,with a CO2/CH4 adsorption ratio at 298 K ranging from 67.2 at 0.2 bar to 17.3 at 1 bar.The small 7- and 8-ring pore openings allow CO2 molecules (3.3 ? kinetic diameter) to enter the channels,but block the larger CH4 molecules (3.8 ? kinetic diameter).This porous material shows a remarkable CO2/CH4 adsorption ratio that is significantly higher than that exhibited by conventional 8-ring pore materials (around 6.0),[3] making it attractive for processes requiring CO2/CH4 separation.