Synthesis and Structure Determination of a New Microporous Zeolite with Large Cavities Connected by Small Pores

A new small-pore germanosilicate zeolite, named as ITQ-49, has been synthesized using a new ditetraalkylphosphonium dication as an organic structure-directing agent, and its structure has been solved by direct methods applied to the powder X-ray diffraction pattern of the calcined solid. This new zeolite crystallizes in the space group Immm with cell parameters a = 19.6007(8) Å, b = 18.3274(7) Å, and c = 16.5335(6) Å. The pore topology of ITQ-49 consists of large, nonspherical cavities that are connected to each other through small eight-membered-ring windows, resulting in a unidirectional small-pore zeolite that has a relatively large adsorption capacity. Also, ITQ-49 contains double four-membered-ring units where Ge is preferentially located, and fluoride anions are placed inside these units.

本研究以一种新型二四烷基鏻双阳离子为有机结构导向剂（organic structure-directing agent），成功合成了一款命名为ITQ-49的新型小孔锗硅酸盐沸石。通过直接解析法对焙烧后样品的粉末X射线衍射（powder X-ray diffraction）图谱进行解析，确定了其晶体结构。该沸石的晶体所属空间群为Immm，晶胞参数分别为a=19.6007(8) Å、b=18.3274(7) Å、c=16.5335(6) Å。ITQ-49的孔道拓扑结构由大型非球形笼腔组成，各笼腔通过小型八元环窗口相互连通，形成一款具有较高吸附容量的单向小孔沸石。此外，ITQ-49的结构中含有双四元环结构单元，锗原子优先占据该单元的晶格位点，且氟阴离子（fluoride anions）填充于这些单元内部。