Generating zeolite crystals with mesoscopic aperiodic structure to promote catalytic hydroisomerization

Abstract

Generating hierarchical zeolites provides an effective way to enhance their transport and catalytic properties. Several seminal methods have been reported to fabricate them with mesoscopic periodic order using surfactant-like structure directing agents (SDAs). Nonetheless, designing SDAs to synthesize unidimensional hierarchical zeolites remains challenging, as their habitual growth along the channel direction is often unaffected by SDAs or growth modifiers. Herein, we report the synthesis of discus-architectured *MRE zeolite built up of crystalline domains registered in a decagonal, aperiodic order with designed polycationic ([–N⁺(CH₃)₂–C₆H₁₂–N⁺(CH₃)₂–C₇H₁₄–]_n[Br⁻]_2n) as a SDA. This hierarchical zeolite has abundant mesopores and exhibits a tenfold electron diffraction pattern similar to that of a quasicrystal due to the directional connection of nanodomains through 10-membered rings serving as rotational centers. The crystallization proceeds through oriented coalescence of polymorph domains with micropore channels normal to the discus. The material exhibits enhanced catalytic n-dodecane hydroisomerization performance, thanks to its strong acidity, reduced micropore channel length and presence of mesopores. The combination of crystalline order within each domain and aperiodic order for their arrangement diversifies structures for hierarchical zeolites and the design of polycationic SDAs expands the toolkit to generate them.