• A template-free, low-temperature synthesis of hierarchical NaX zeolite from natural kaolinite is demonstrated, offering an energy-saving and environmentally friendly route.
• The hierarchical NaX zeolite exhibits both inter- and intra-crystalline mesopores, smaller crystal size, and larger external surface area than commercial NaX, enhancing accessibility for bulky molecules.
• The synthesized catalyst shows significantly improved catalytic performance in Knoevenagel condensation, attributed to reduced diffusion limitations and increased active site accessibility.
• This work provides a cost-effective strategy for constructing hierarchical zeolites, with potential for broad application in fine chemical manufacturing.