Numerous studies have reported the synthesis of hierarchical porous zeolites generally by using template methods (soft-template and hard-template method) [
20–
24] and post-processing methods (dealumination or desilication) [
25–
28]. However, etching through dealumination or desilication damages the zeolite framework structure [
29–
31]. Furthermore, the surfactants required by the soft-template method also incur limitations due to their complex nature and high cost [
32,
33]. The hard-template method is not only simple and efficient but also preserves the framework structure of zeolites [
34]. Notably, the hard-template method was proven to create ordered mesoporous structures and precisely control mesopore size. Wang et al. [
35] applied three-dimensionally ordered mesoporous carbon (20, 40 and 80 nm) as a template to obtain hierarchical SAPO-34 zeolites with a three-dimensionally ordered mesoporous-imprinted structure, and the ordered mesopore size could be tuned from 5.5 to 13.0 nm by varying the size of the three-dimensionally ordered carbon (from 20 to 80 nm). Based on the generalized Murray’s law on the design of suitable pore size, our group designed an
in-situ crystallization approach for constructing hierarchical single-crystal MFI zeolites by using ordered mesoporous carbon-silica composite as a hard template. The as-prepared hierarchical single-crystal ZSM-5 zeolites were fabricated from zeolite nanocrystals, which offer improved catalytic properties and higher stability in the cracking reaction of isopropyl benzene [
36]. In addition to introducing mesopores into zeolite catalysts, the adjustable Si/Al ratio is also an indispensable factor to evaluate the physical and chemical properties of hierarchical single-crystal ZSM-5 zeolites. Considerable studies have controlled the Si/Al ratio in zeolites to investigate its catalytic capacity [
37–
39], but few studies have shown that the Si/Al ratio of ZSM-5 zeolites can affect catalytic performance by changing the acidity and the density of micropores present in the zeolite framework. The bare benzyl alcohol (BA) self-etherification reaction [
40] was the optimal probe reaction, which is an important reaction in the production of pharmaceutical intermediates and fine chemicals and an environmentally friendly reaction with water as a by-product [
41]. Note that 2,6-di-tert-butylpyridine (DTBP) may be added in another BA self-etherification reaction to poison the active sites on the surface of the zeolites, so that only the active sites inside the zeolitic micropores could contact the BA and participate in the reaction. The comparison of these reactions can be used to demonstrate the benefits of hierarchical single-crystal ZSM-5 zeolites and verify how the Si/Al ratio affects its catalytic performance.