Floating Synthesis of Porous Coordination Crystals With Absorption Capability Reinforcement

ZIF-67 was containerlessly synthesized via acoustic levitation for superior absorption performance. The acoustic streaming accelerated the solute diffusion, and the acoustic cavitation effectively promoted the coordination of Co²⁺ and pyridine N in the synthesis. This speeded up the nucleation and growth of ZIF-67 nanoparticles, refined the particles and improved the dispersion. The smaller particle and the larger Zeta potential improved the adsorption performance of ZIF-67 synthesized in the acoustically levitated aqueous-phase droplet for methyl orange. Accordingly, the adsorption rate and saturated adsorption capacity of ZIF-67 synthesized in water solution were increased by 3.5 times and 25.8% respectively, compared with ordinary condition. Besides, the Co@CNTs prepared by ZIF-67 from acoustic levitation synthesis exhibited a 16 dB decrease in reflection loss and a 0.6 GHz increase in effective bandwidth, which is ascribed to the enhanced coordination of Co²⁺ and pyridine N, which contributed to the stronger catalytic effect on the carbon source, thus improving the electromagnetic wave absorption intensity owing to the enhanced diploe polarization loss. Besides, the increase in Co²⁺ amount produced more lattice defects, consequently enhancing the interfacial polarization loss. This synthetic strategy provides a pathway for developing porous nanometal materials by manipulating coordination to enhance their electromagnetic absorption ability for practical applications.