Achieving efficient room-temperature catalytic H2 evolution from formic acid through atomically controlling the chemical environment of bimetallic nanoparticles immobilized by isoreticular amine-functionalized metal-organic frameworks

From the viewpoint of controlling the catalytic performance of supported metal nanoparticles (NPs) through tuning their chemical environment in the atom level, we have used electron-donating amino groups and three organic amine molecules to modify the organic linkers and unsaturated coordination Cr3+ sites in one porous metal-organic framework MIL-101 with atomically precise structures, respectively, and then we have prepared a series of AuPd NPs immobilized by the two types of functional MIL-101 supports. The as-synthesized AuPd NPs were used for the catalytic dehydrogenation of formic acid (HCOOH) and the results showed that these catalysts exhibited remarkably different activities and H-2 selectivities at 298 K. Particularly, the AuPd NPs immobilized by MIL-101-NH2 presented 100% of H2 selectivity and the highest activity because of the synergistic steric and electronic effects, which were related to the activation of HCOOH and enrichment of electron density of active Pd species. The investigation of UV-vis spectroscopy showed that the reaction between the mixed metal ions (AuCl4- and PdCl42-) and the four functional MIL-101 supports generated four different coordination complex intermediates, which played an important role in yielding AuPd NPs with different chemical environment and inducing different catalytic performance. (C) 2017 Elsevier B.V. All rights reserved.