Germanosilicate UTL and its rich chemistry of solid-state transformations towards IPC-2 (OKO) zeolite

The unique features of the germanosilicate zeolite possessing the UTL framework topology offer various post-synthetic modifications such as ‘top-down’, ‘inverse sigma’ or solid-state transformations. The presented work describes several different synthetic routes generating the IPC-2 type zeolite (OKO topology) utilizing UTL as the parent material. In total, five approaches were investigated which exhibit this topological transformation from germanosilicate UTL to OKO type material: (1) alkoxysilylation of the layered precursor (IPC-1P) formed by hydrolysis of UTL; (2) direct conversion of UTL by treatment in 7–12 M hydrochloric acid; (3) direct transformation under mild conditions of water and ammonium nitrate solution on Al- and B-UTL; (4) repeated calcinations of boron-containing UTL; (5) using organic solutions as self-stabilization agents. Resulting materials were examined by powder XRD, nitrogen sorption, SEM and EDX. Briefly, all the materials possessed the same OKO topology but had differing BET surface areas and micropore volumes in the ranges of 201–493 m²/g and 0.095–0.189 cm³/g, respectively. The morphologies of crystals were very similar, while the size of them varied between 10 and 50 μm. The main goal of the study was to emphasize the complexity of post-synthetic UTL zeolite chemistry and the diverse range of solid-state transformations possible.