Phase engineering is arising as an attractive strategy to tune the properties and functionalities of nanomaterials.In particular,amorphous/crystalline heterophase nanostructures have exhibited some intriguing properties.Herein,the one-pot wet-chemical synthesis of two types of amorphous/crystalline heterophase Pd Cu nanosheets is reported,in which one is amorphous phase-dominant and the other one is crystalline phase-dominant.Then the aging process of the synthesized Pd Cu nanosheets is studied,during which their crystallinity increases,accompanied by changes in some physicochemical properties.As a proof-of-concept application,their aging effect on catalytic hydrogenation of 4-nitrostyrene is investigated.As a result,the amorphous phase-dominant nanosheets initially show excellent chemoselectivity.After aging for 14 days,their catalytic activity is higher than that of crystalline phase-dominant nanosheets.This work demonstrates the intriguing properties of heterophase nanostructures,providing a new platform for future studies on the regulation of functionalities and applications of nanomaterials by phase engineering.