Formation and stabilization of colloidal ultra-small palladium nanoparticles on diamine-modified Cr-MIL-101: Synergic boost to hydrogen production from formic acid.

Ultra-small nano-sized palladium particles were successfully stabilized within the pores of diamine groups grafted open metal site metal-organic frameworks of Cr-MIL-101; coordinated diamine groups of ethylene diamine (ED) and propyl diamine (PD) on the active site of chromium units of Cr-MIL-101. The physiochemical properties of the Pd@Cr-MOFs were investigated using FTIR, XRD, SEM/EDX mapping, TEM, BET, and AAS. The Cr-MIL-101 stabilized ultra-small Pd nanoparticles, Pd@(ethylene diamine)/Cr-MIL-101, and Pd@(propyl diamine)/Cr-MIL-101, displayed catalytic activity for clean dehydrogenation of formic acid and generation of hydrogen at room temperature. The resultant Pd@ED/Cr-MIL-101 catalyst indicates high catalytic activity with turnover frequency (TOF) of 583 h-1 at 328 K, which is superior to most of the reported catalysts, including Pd@PD/Cr-MIL-101 with TOF 532 h-1. Our studies open up a new method to the design of an ultra-small metal nanoparticle for the catalytic dehydrogenation of HCOOH.