Additive-mediated regulation of fractal evolution and anisotropic b-axis growth from amorphous aluminosilicates to disordered lamellar clinoptilolite

Additive-mediated interfacial regulation governs clinoptilolite crystallization. • Fractal evolution from amorphous precursors to lamellar structures is elucidated. • Surfactant-induced solvation layers suppress anisotropic b -axis growth. : Additive-mediated regulation provides an effective strategy for controlling zeolite crystallization pathways and anisotropic crystal growth. Herein, using o-phenylenediamine (OPD), cetyltrimethylammonium bromide (CTAB), and polyethylene glycol (PEG) as representative additives, the structural evolution of HEU-type clinoptilolite (CP) from amorphous aluminosilicate nanoparticles to disordered platelet architectures is systematically investigated. Small-angle x-ray scattering combined with x-ray diffraction patterns, Fourier transformed infrared and Raman spectra, N 2 adsorption-desorption isotherms, and scanning/transmission electron microscopy images, revealed the fractal evolution of the aluminosilicate species and the formation of hydrated interfacial solvation layers during the growth periods of the hydrothermal crystallization. The results showed that additive-induced hydrated solvation layers suppressed amorphous nanoparticle attachment, reduced surface roughness, and inhibited the ordered HEU framework assembly. The interfacial layer thickness followed the order CTAB-CP (∼2.5 nm) > OPD-CP (∼1.2 nm) > PEG-CP (∼0.8 nm), corresponding to progressively weaker inhibition of crystal growth. Prolonged nucleation was conducive to promoting the formation of the primary building structural units and HEU nanocrystal nuclei, accelerating the generation of the disordered platelet morphologies during the growth stage. Meanwhile, the hydrated solvation layers hindered the framework rearrangement and suppressed anisotropic crystal growth along the b -axis, with inhibitory strength following CTAB > OPD > PEG. Molecular simulations further supported facet-dependent additive adsorption as a key factor influencing anisotropic growth kinetics. CO 2 /CH 4 /N 2 adsorption measurements showed that interfacial regulation affected gas diffusion and adsorption behavior. Overall, these results are consistent with a crystallization pathway in which particle-attachment contributions coexist with classical monomer addition, providing insight into additive-controlled platelet zeolite growth. Download: Download high-res image (374KB) Download: Download full-size image