Defective plane induced fractal TON zeolites for efficient hydroisomerization of long-chain hydrocarbons

Abstract

Fractal crystals are a class of fascinating crystals in this world, typically captured in dense crystal phases like snowflakes, graphene, and metal alloys. Nevertheless, such crystal analogues are quite rare in framework crystal phases, and their structural origins remain an intriguing enigma. In this work, we successfully constructed a series of fractal TON zeolites via a rare twinning mode, thereby revealing their structural origins. The continuous rotational electron diffraction technique solved its unique crystallographic structure. The fractal boundary exhibited coherence along the {021} facets and left the periodic dangling silanol defects. As evidenced by spatial element reconstruction and structural analysis, we found that the TON fractal was triggered by organic cations anchoring heteroatoms at the framework T3 site. Such fractal dimensions of TON can be effectively tailored by adjusting the heteroatom concentration in the synthetic system. The Pt-loaded fractal TON zeolite bifunctional catalyst demonstrated remarkable performance in the hydroisomerization of n-hexadecane with a maximum isomer yield of 84.4%, which is 28.9% higher than that of the Pt/rod-like TON catalyst, attributed to the more accessible active sites of the fractal architecture. Unravelling the twinning structure and its origin of zeotype catalysts would afford novel insights for the development of promising advanced heterogeneous catalysts.