In Situ Amine Formation to Modulate MOF-Derived PdIn N-Doped Carbon Catalysts

Metal-Organic Frameworks (MOFs) are versatile precursors for developing heteroatom-doped carbon-supported catalysts with complex structures and functionalities. In this work, we rationalize an amine-mediated approach that combines a mild chemical pretreatment with pyrolysis to direct the transformation of a PdIn-MOF precursor into dispersed PdIn intermetallic nanoparticles supported on N-doped carbon. Advanced characterization techniques, including synchrotron ex situ and in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD), demonstrate that the chemical pretreatment, involving in situ amine generation under reductive conditions, facilitates the early formation of Pd nanoparticles. This pre-nucleation influences the kinetics of intermetallic phase formation during the subsequent pyrolysis, promoting a more regulated alloying process. Systematically varying nitro precursors and solvents shows that amine sterics and basicity govern nanoparticle size, phase development, PdIn ratio, nitrogen doping, and surface area. Finally, catalytic evaluation in alkyne semihydrogenation shows that the family of PdIn catalysts thus prepared achieves outstanding selectivity and high productivity, outperforming benchmarking Pd/C and Lindlar catalysts across diverse substrates. Specifically, materials synthesized using ethanol and amines with low pKb values offer superior control over particle formation and catalytic behavior. Overall, these findings establish and explain a modular strategy for designing next-generation bimetallic catalysts for selective hydrogenation applications via MOF-derived syntheses.