Amine-directed syntheses and crystal structures of phosphate-based zeolite analogs

Abstract

A large number of zeolite analogs including two chabazite structures with a Co/Al ratio of 2 have been synthesized by the use of linear, branched and cyclic amines with different charges and geometries in the cobalt (or zinc or magnesium) aluminophosphate system. The incorporation of divalent metal atoms into the framework metal-atom sites is directly established through the occupancy refinement and the lengthening of metal–oxygen bond distances using single-crystal diffraction data. Host–guest charge density matching as an important synthesis parameter is demonstrated by the correlation between the Co/Al ratio and the charge/volume ratio of protonated amines. The successful synthesis of these new phases supports the concept that the multidimensionality of the channel system is closely associated with relatively highly charged framework structures. The ease with which chabazite analogs crystallize under a diversity of different conditions suggests that more chabazite analogs can be formed with other amines.