Ternary Alloys Encapsulated within Different MOFs via a Self-Sacrificing Template Process: A Potential Platform for the Investigation of Size-Selective Catalytic Performances

Abstract

Functional nanoparticles encapsulated within metal-organic frameworks (MOFs) as an emerging class of composite materials attract increasing attention owing to their enhanced or even novel properties caused by the synergistic effect between the two functional materials. However, there is still no ideal composite structure as platform to systematically analyze and evaluate the relation between the enhanced catalytic performance of composites and the structure of MOF shells. In this work, taking RhCoNi ternary alloy nanoflowers, for example, first the RhCoNi@MOF composite catalysts sheathed with different structured MOFs via a facile self-sacrificing template process are successfully fabricated. The structure type of MOF shells is easily adjustable by using different organic molecules as etchant and coordination reagent (e.g., 2,5-dihydroxyterephthalic acid or 2-methylimidazole), which can dissolve out the Co or Ni element in the alloy template in a targeted manner, thereby producing ZIF-67(Co) or MOF-74(Ni) shells accordingly. With the difference between the two MOF shells in the aperture sizes, the as-prepared two RhCoNi@MOF composites preform distinct size selectivity during the alkene hydrogenation. This work would help us to get more comprehensive understanding of the intrinsic role of MOFs behind the enhanced catalytic performance of nanoparticle@MOF composites.

Keywords: composite catalysts; hydrogenation; metal−organic frameworks; self-sacrificial template.