Transcrystallization of X zeolite into SSZ-39 for enhanced NH3-SCR catalysis through tailored Brønsted acid sites and Cu species.

Traditional synthesis of SSZ-39 zeolites via Y zeolite precursors faces challenges of high cost, complex dealumination, and limited scalability. Here, we present a pioneering interzeolite conversion (IZC) strategy using low-cost X and A zeolites as precursors, bypassing the need for pretreatments. A new crystallization mechanism centered on sodalite cages is proposed, supported by theoretical calculations. The synthesized SSZ-39 zeolites exhibit excellent crystallinity and well-defined pore structures. The strong Brønsted acid sites and [Cu(OH)]+ species in Cu-X-SSZ-39 both contribute to its outstanding NO x conversion performance, maintaining a remarkable 97% conversion even at the high temperature of 600 °C. In situ dual-beam Fourier transform infrared (DB-FTIR) studies confirm the rapid depletion of Cu-NO3 - on Cu-X-SSZ-39, highlighting the superior redox dynamics. This work not only advances the mechanistic understanding of zeolite transformations but also establishes a scalable, eco-friendly route for designing high-performance NH3-SCR catalysts with industrial potential.