Efficient supported noble metal-based nanocatalysts are attracting considerable attention for heterogeneous catalysis and environmental remediation. Metal-organic framework (MOF) with high surface area and well-isolated pore channels limit the aggregation of the nanoparticles and are known as promising templates for synthesizing nanoparticles with controllable sizes and dispersity. Present work accounts, polydopamine modified-MOF assisted controlled growth of ultrafine bimetallic nanoalloy followed by the structural and morphological characterization using PXRD, FT-IR, TGA, UV-Visible spectroscopy, X-ray photoelectron spectroscopy, N2 adsorption/desorption isotherm, etc. Morphological micrographs are evident of aggregation of nanoparticles with low metal loading for uncoated MOF. Palladium and Silver nanoalloys (Pd NPs and Ag NPs) immobilized on the polydopamine modified MOF with a narrow size distribution (2.3 ± 0.2 nm). Density functional theory calculation, shifting in binding energy value of corresponding elements in XPS and absence of Ag plasmon spectra in UV-Vis spectra further suggests AgPd nanoalloy formation. The nanocatalyst shows excellent heterogeneous catalytic activity with high turnover frequency in formic acid dehydrogenation, aldehyde hydrogenation, Suzuki–Miyaura coupling and batch and continuous nitrophenol reduction reaction under ambient conditions with low catalyst loading. The synthesized catalyst showed high catalytic efficiency for nitrophenol reduction with a higher turnover frequency 3200 h-1. Also, the TOF values for the dehydrogenation of formic acid at 55 and 25 °C as high as 4600 and 430 h-1, respectively, which are 2-fold higher than the catalyst supported without PDA coating. DFT calculations show that the bimetallic nanoparticle on PDA-coated MOF has a better selectivity/activity for FA dehydrogenation by following a lower energy path for hydrogen desorption, consistent with the experimental results. More appreciably, this catalyst is stable and easily recycled without losing any catalytic activity.

Synergistic ultrafast heterogeneous catalysis by finely dispersed Ag-Pd bimetallic nanoalloys immobilized on polydopamine modified metal-organic framework

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