Construction of the mosaic aluminophosphate zeotypes based on nonclassical crystallization and in situ selective etching strategies

Owing to short diffusion lengths and more accessible active sites, hierarchical zeolitic materials can substantially improve catalytic activities and lifetimes compared to the conventional counterparts. Here we develop a straightforward and mesopore-template-free strategy to prepare aluminophosphate-based LTA zeotypes with mosaic architectures and hierarchical porosities. The influence of synthesis parameters and time-dependent study on the crystallization process were studied comprehensively using multiple techniques. The results demonstrate that the mosaic architectures were formed based on nonclassical crystallization, i.e., phase transformation of a lamellar phase to aligned crystalline AlPO4-42 nanoparticles followed by crystal fusion, and in situ selective etching of grain boundaries and defects. Meanwhile, heteroatom-substituted AlPO4-42 zeotypes with the mosaic morphologies can also be synthesized, which show enhanced ideal adsorbed solution theory (IAST) selectivities and efficient dynamic separation performances in the CO2/N2 mixture. This work not only provides a novel mesoporogen-free strategy for the preparation of hierarchical zeotypes, but also sheds new insight into the crystallization pathway.