Remodeling nanodroplets into hierarchical mesoporous silica nanoreactors with multiple chambers

Abstract

Multi-chambered architectures have attracted much attention due to the ability to establish multifunctional partitions in different chambers, but manipulating the chamber numbers and coupling multi-functionality within the multi-chambered mesoporous nanoparticle remains a challenge. Herein, we propose a nanodroplet remodeling strategy for the synthesis of hierarchical multi-chambered mesoporous silica nanoparticles with tunable architectures. Typically, the dual-chambered nanoparticles with a high surface area of ~469 m² g^-1 present two interconnected cavities like a calabash. Furthermore, based on this nanodroplet remodeling strategy, multiple species (magnetic, catalytic, optic, etc.) can be separately anchored in different chamber without obvious mutual-crosstalk. We design a dual-chambered mesoporous nanoreactors with spatial isolation of Au and Pd active-sites for the cascade synthesis of 2-phenylindole from 1-nitro-2-(phenylethynyl)benzene. Due to the efficient mass transfer of reactants and intermediates in the dual-chambered structure, the selectivity of the target product reaches to ~76.5%, far exceeding that of single-chambered nanoreactors (~41.3%).

Fig. 1. Calabash-like mesoporous silica nanoparticles.

a SEM, b, d, e TEM, and c dark-field TEM images of the dual-chambered mesoporous silica nanoparticles with different magnifications; Inset of c is the corresponding distribution histograms of the particle body lengths. f The structural model, and g element mappings of the mesoporous nanoparticle; h Nitrogen sorption isotherms, and the pore size distribution (inset of h) of the mesoporous silica nanoparticle. A total of 504 nanoparticles are analyzed. Source data are provided as a Source Data file.

Fig. 2. Hierarchical multi-chambered mesoporous silica nanoparticles with tunable chamber numbers.

a, d, g The illustration of the nanodroplet remodeling process. By controlling the number of the THF additions, the chamber numbers can be tuned from one to three. b, e, h TEM images and c, f, i the distribution histograms of the outer diameter of the hierarchical multi-chambered mesoporous silica nanoparticles with a variable number of chambers: b, c single-chamber, e, f dual-chambers, and h, i tri-chambers. Insets in b, e, and h are the structural models of mesoporous silica nanoparticles. Source data are provided as a Source Data file.

Fig. 3. Hierarchical multi-chambered mesoporous nanoparticles with tunable opening and chamber distribution.

a–c Structural models, TEM images, and d the corresponding distribution histograms of the body length of the multi-chambered mesoporous nanoparticles with tunable openings; a single-chamber, b dual-chambers, c tri-chambers. e–g Structural models and TEM images of the dual-chambered nanoparticles with tunable chamber distance. h The relative changes of center distance and the diameter of the second chamber. Error bars represent standard deviation. Source data are provided as a Source Data file.

Fig. 4. Selectively in situ assembly of different functional units.

a Schematic illustration of the selective in situ loading of hydrophilic nanoparticles in different chambers. b SEM, c–e TEM, and f element mapping images of the dual-chambered mesoporous nanoparticle with Pt loaded in the upper and magnetic Fe₃O₄ nanoparticles anchored in the bottom chambers. Insets in f are the structure model of the nanocrystal-loaded mesoporous dual-chambered nanoparticles.

Fig. 5. Dual-chambered mesoporous silica nanoreactors.

a SEM, b HAADF-STEM, and c high-resolution TEM (HRTEM) images of the obtained dual-chambered mesoporous silica nanoreactors by selectively loading Au and Pd nanocrystals in the bottom and upper cavities of reactors, respectively. The inset in b is the 3D structural model and inset in c is the HRTEM image of the Pd nanocrystals. d Schematic illustration, e concentration distribution of reactants, and f kinetic plots of the cascade reaction in the dual-chambered nanoreactor (Au in the bottom chamber, Pd in the upper chamber). g Kinetic plots of the cascade reaction in the single-chambered nanoreactor (Au and Pd loaded in the same chamber). h The selectivity to 2-phenylindole as a function of time. i The yield and selectivity of 2-phenylindole under different catalysts: mixed-Au and Pd in single-chambered silica particles (Catalyst 5), mixed-Au and Pd nanocrystals (Catalyst 6), mixed-catalyst 1 and 2 (Catalyst 7), mixed-Au and Pd on dense silica spheres (Catalyst 8), and spatial separation of Au and Pd in dual-chambered silica particles (Catalyst 9), respectively. Note: in the cascade synthesis of 2-phenylindole, the autoclave was purged with hydrogen gas at least three times and the H₂ pressure was set to 1.5 MPa. The temperature was kept at 80 °C. Source data are provided as a Source Data file.

Fig. 6. Finite element analyses of the mass transfer in the nanoreactors with different morphologies.

a, d The simulated transient-state concentration gradient of the reactants in different nanoreactors at 20 µs. b, e The corresponding total flux profiles of reactants in single- and dual-chambered nanoreactors at 20 µs. Position A is the opening of the nanoreactor, Position B is the center location of the upper chamber, Position C is the middle of the whole cavity, and Position D is the center location of the bottom chamber. c The calculated transient-state concentration gradient of the reactants at 20 µs at different positions of the nanoreactors. f The concentration distribution as a function of diffusion distance (different position) at 20 µs. The diffusion of reactants to the bottom chamber is specified as the positive direction. The simulations were performed in a time-dependent mode at a microsecond scale due to the rapid evolution of physical fields. Source data are provided as a Source Data file.

Fig. 7. The illustration of the nanodroplet remodeling strategy.

The formation process of the multi-chambered mesoporous silica nanoparticles. The multi-chambered nanoparticles can be fabricated by adding solvents with certain oil–water distribution coefficients (e.g., THF) at different stages.