Finely dispersed AgPd bimetallic nanoparticles on a polydopamine modified metal organic framework for diverse catalytic applications

Abstract

An efficiently supported noble metal-based heterogeneous catalyst with ultrafine dispersion and small size for multifunctional catalysis and pollutant degradation is highly desirable. In this work, a polydopamine modified-MOF (MIL-125-NH2) template has been used to synthesize ultrafine silver-palladium (AgPd) bimetallic nanoparticles. The characterization results confirm the formation of well-dispersed ultrafine bimetallic nanoparticles with a narrow size distribution (2.2 ± 0.3 nm). The prepared catalyst exhibits excellent heterogeneous catalytic activity with high turnover frequency in batch and continuous nitrophenol reduction, aldehyde hydrogenation, formic acid dehydrogenation (in the presence of additive sodium formate), and Suzuki–Miyaura coupling reaction at ambient conditions. Moreover, its high stability makes it a durable catalyst system for multicycle use after recycling or in a continuous flow reactor. The rate of hydrogen production using AgPd@MIL-125-NH2-PDA is many orders of magnitude higher than that of uncoated and monometallic (Ag or Pd) nanoparticles on MOF. Additionally, density functional theory (DFT) calculations provide an insight mechanism for each FA dehydrogenation step and show that the bimetallic nanoparticle on PDA coated MOF has better selectivity towards FA dehydrogenation by following a lower energy path for hydrogen desorption. These findings highlight the advantages of rational template modification in synthesizing finer bimetallic nanoparticles, which can open up many new avenues for designing metal nanoparticle-MOF-based composite materials for a variety of potential applications.