2024 AIChE Annual Meeting

Synthesizing Platinum Nanoparticles on Metal Organic Frameworks

Metal organic frameworks (MOF) are relatively new in the science of catalysis. With high internal surface area and structural stability, they are being explored as supports for supported metal catalysts. To date, the preparation method of Strong Electrostatic Adsorption (SEA), which has been widely applied to synthesize metal nanoparticles on numerous oxide and carbon supports, has not been applied to MOFs. SEA is a method that produces extremely small nanoparticles by exploiting the surface chemistry of the support to induce electrostatic attraction between charged surfaces and oppositely charged metal precursor complexes. This is done by controlling the pH of a metal precursor solution in relation to the support’s point of zero charge (PZC).

We hypothesize that SEA can be used to synthesize ultrasmall platinum nanoparticles on carbon supports derived from MOF materials, when the support pore size becomes large enough to allow the internal diffusion of the hydrated metal precursors. To test this hypothesis, we are comparing metal uptake and reduced metal particle size over three different MOF-derived materials with increasing pore size distributions. These materials all have high PZCs, and the adsorption of anionic Pt chloride precursors has been measured in the low pH range. The metal nanoparticle size has been characterized by powder x-ray diffraction (XRD) and scanning transmission electron microscopy (STEM).

Preliminary results reveal metal adsorption trends among the three MOF materials consistent with significant diffusion limitations, but all materials given rise to very small Pt nanoparticles at relatively high Pt weight loadings.