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Construction of Three-Dimensional Dendritic Hierarchically Porous Metal−Organic Framework Nanoarchitectures via Noncentrosymmetric Pore−Induced Anisotropic Assembly
Summary:
The authors from Jilin University (China) and The University of Queensland (Australia) developed 3D dendritic hierarchically porous UiO-66 MOF nanoarchitectures with controllable structural symmetry and multi-scale porosity, achieving enhanced catalytic activity in CO₂ cycloaddition reactions.
Background:
1. To address the mass diffusion limitation of conventional microporous MOF catalysts (which restricts active site utilization), previous researchers constructed hierarchically porous MOFs. However, these works lacked a general method to achieve controllable symmetric/asymmetric nanoarchitectures and macro/mesoporous channels for dendritic MOFs.
2. The authors proposed a noncentrosymmetric pore-induced anisotropic assembly strategy, successfully synthesizing UiO-66 MOFs with tunable structures and pores, and verifying its generality in Zr-based UiO-66.
Research Content:
1. Synthesis
-UiO-66 DHPNPs: Used soft template (P123)-assisted self-assembly; dissolved P123 in deionized water, added acetic acid and TMB to form microemulsion, then mixed with (NH₄)₂Ce(NO₃)₆ and BDC, stirred at 800 rpm, 45 °C for 50 min, followed by centrifugation, washing, and drying. Adjusted P123 dosage (0–83.3 mg) or temperature (30–55 °C) to tune structures/pores.
-Microporous UiO-66 NCs: Synthesized without P123, other conditions same as above.
-Zr-based UiO-66: Used P123/F127 as templates, ZrOCl₂·8H₂O and NH₂-BDC as precursors, stirred at 40 °C for 12 h.
2. Characterizations:
1.BET & Pore Size: UiO-66 DHPNPs-45 had BET surface area 545 m²/g, pore volume 1.6 cm³/g; BJH pore size distributed in meso/macro range (35–130 nm by tuning temperature).
2.SEM/TEM: UiO-66 DHPNPs-45 showed spherical morphology (≈920 nm diameter) with radial dendritic nanosheets; particle size tuned to 80–1150 nm by adjusting acetic acid/ligand dosage.
3.Other Tests: XRD confirmed UiO-66 crystalline phase; XPS showed Ce³⁺/Ce⁴⁺ ratio 42.9:57.1 (higher than microporous NCs’ 35.4:64.6); TG showed 5.0 wt% higher weight loss than NCs.
3. Application
-CO₂ Cycloaddition: UiO-66 DHPNPs-45 achieved 97.4% yield (vs. 67.9% for microporous NCs); maintained stability over 5 cycles (slight yield decrease); showed high yields (84.2%–100.0%) for various epoxides.
4. Mechanism
-Formation Mechanism: Initial conelike P123/MOF mesostructure formed, followed by anisotropic nucleation of spherical nanocones; low viscosity promoted radial growth, increasing viscosity accelerated polar angle growth, finally forming isotropic spheres.
-Catalytic Mechanism: Hierarchical pores enhanced mass transport; higher Ce³⁺ exposure provided more accessible Lewis acid sites, boosting catalytic activity.
Outlook:
This research innovatively solves the structural regulation challenge of dendritic MOFs, provides a universal synthesis strategy for complex porous MOFs, and promotes their application in heterogeneous catalysis (e.g., CO₂ conversion), with significant implications for green chemistry and material design.
Construction of Three-Dimensional Dendritic Hierarchically Porous Metal−Organic Framework Nanoarchitectures via Noncentrosymmetric Pore−Induced Anisotropic Assembly
Authors: Tianyu Wu, Guangrui Chen, Ji Han, Ruigang Sun, Bin Zhao, Guiyuan Zhong, Yusuke Yamauchi, Buyuan Guan
DOI: 10.1021/jacs.3c03029
Link: https://pubs.acs.org/doi/10.1021/jacs.3c03029
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