ABSTRACT
Porous oxide materials are of signicant industrial, commercial, and academic interest for their ability to selectively recognize, accommodate, and interact with guest species in their pores and channels.1 Ongoing research has been focused on the development of novel materials with diverse pore features for various applications.2 One particular interest involves the synthesis of ordered crystalline oxide frameworks with low framework density and extra-large pores (>12-ring).3 Such materials have the potential to selectively adsorb, separate, or catalyze large molecules spanning from 10 to 20 Å.4 However, zeolitic silicates and aluminosilicates have shown limitations in ring size, with the largest observed ring being the 14-ring in CIT-55,6
11.1 Introduction .................................................................................................. 319 11.1.1 Composite Building Units ................................................................ 320
11.2 Synthesis ....................................................................................................... 322 11.2.1 Structure-Directing Agents .............................................................. 327 11.2.2 Framework Elements ........................................................................ 331 11.2.3 Heating Conditions ........................................................................... 332 11.2.4 Solvents ............................................................................................. 333 11.2.5 Mineralizing Agent ........................................................................... 333
11.3 Structures ...................................................................................................... 334 11.3.1 Germanium-Containing Zeolites with Double-4-Rings
and 3-Rings ....................................................................................... 334 11.3.2 Ge7 Phases ......................................................................................... 336 11.3.3 Ge9 Phases ........................................................................................ 337 11.3.4 Ge10 Phases........................................................................................ 338 11.3.5 Mixed Cluster Germanates ...............................................................340
11.4 Applications .................................................................................................. 341 11.5 Conclusions ................................................................................................... 345 Acknowledgments ..................................................................................................346 References ..............................................................................................................346
and UTD-17 (CFI and DON zeolite framework types respectively).8 Mesostructured materials have pore diameters ranging from 15 to 100 Å; however, the walls of these frameworks are amorphous.9
