Acoustic Microreactor-Enabled Controllable Production of Porous Microspheres toward Efficient Confined Catalysis

Porous microspheres with well-defined size and tailored morphology have garnered significant attention in the catalytic field due to their unique properties. However, the size, pore distribution, and morphology of these microspheres are difficult to control in traditional batch reactors. Herein, an efficient microfluidic strategy was proposed to produce porous polystyrene (PPS) microspheres, in which the PPS microspheres with adjustable pore size and controllable morphology were fabricated in a flower-like acoustic microreactor by readily altering the operating conditions. The effects of flow rates, ternary phase composition, residence time, and input voltage were investigated comprehensively. The results demonstrated that pore size could be flexibly regulated from 176 to 354 nm by adjusting the operating parameters. 5.3 wt % Ag nanoparticles were stabilized in the PPS microspheres for the 4-nitrophenol (4-NP) reduction reaction into 4-aminophenol (4-AP) efficiently. The pseudo-first-order reaction rate constant and activity parameter were 1.18 × 10^-2 s^-1 and 1180 s^-1·g^-1, respectively. The catalytic activity and stability were maintained after five cycles, and the turnover frequency (TOF) with Ag@PPS microspheres for the reduction of 4-NP was calculated to be 907.78 h^-1. These results not only provide a facile strategy for porous microspheres controllable preparation but also offer a confined microenvironment to degrade organic pollutants in aqueous environments efficiently, which is beneficial for water environment management.