Towards mass production of Au nanoparticles supported on montmorillonite microspheres for catalytic reduction of 4-nitrophenol

Noble metals supported on substrates have been proven as highly efficient catalysts for the reduction of nitrocompounds. However, their large-scale applications are still limited by the problems of fouling and transport during the mass production process. Herein, we first fabricated a spherical montmorillonite (Mt) substrate via spray drying technique, followed by the deposition of Au NPs through polydopamine chemistry to synthesize spherical Au nanoparticles supported Mt (Au@Mt) microspheres. The Au loading is 14.5 wt%, whereas the specific surface area of the Au@Mt microspheres is 47.3m2 g−1, endowing the prepared Au@Mt microspheres with excellent catalytic activity to the reduction of 4-nitrophenol (4-NP) in the presence of NaBH4 with the optimized apparent reduction rate constant higher than 1.05 min−1. Furthermore, the microspheres can be easily recycled with self-sedimentation without any devices involved and showed excellent stability and recyclability for at least 20 cycles without almost unchanged spherical morphology and catalytic performance. Our straightforward strategy to solve the issue of the mass production process through granulation of amorphous nanomaterial substrate facilitates the practical application of these catalysts in the reduction of nitro-compounds.

负载于基底的贵金属已被证实是硝基化合物还原反应的高效催化剂。然而，其大规模应用仍受限于大规模生产过程中的积垢与传质问题。本研究首次采用喷雾干燥技术制备球形蒙脱石（montmorillonite, Mt）基底，随后通过聚多巴胺化学法负载金纳米颗粒（Au NPs），合成了金纳米颗粒负载蒙脱石（Au@Mt）微球。该微球的金负载量为14.5 wt%，比表面积达47.3 m²·g⁻¹，因此在硼氢化钠（NaBH₄）存在下对对硝基苯酚（4-nitrophenol, 4-NP）的还原反应展现出优异催化活性，优化后的表观还原速率常数高于1.05 min⁻¹。此外，该微球可通过自然沉降实现便捷回收，无需额外设备，且在至少20次循环测试中保持优异的稳定性与循环性能，其球形形貌与催化性能几乎无变化。本研究提出的通过非晶纳米材料基底造粒的简便策略，解决了大规模生产难题，可为这类硝基化合物还原催化剂的实际应用提供可行路径。