Rational coupling of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts is extremely important for practical overall water splitting,but it is still challenging to construct such bifunctional heterostructures.Herein,we present a metal-organic framework (MOF)-etching strategy to design free-standing and hierarchical hollow CoS2-MoS2 heteronanosheet arrays for both HER and OER.Resulting from the controllable etching of MOF by MoO42-and in-situ sulfuration,the obtained CoS2-MoS2 possesses abundant heterointerfaces with modulated local charge distribution,which promote water dissociation and rapid electrocatalytic kinetics.Moreover,the two-dimensional hollow array architecture can not only afford rich surface-active sites,but also facilitate the penetration of electrolytes and the release of evolved H2/O2 bubbles,Consequently,the engineered CoS2-MoS2 heterostructure exhibits small overpotentials of 82 mV for HER and 266 mV for OER at 10 mA cm-2.The corresponding alkaline electrolyzer affords a cell voltage of 1.56 V at 10 mA cm-2 to boost overall water splitting,along with robust durability over 24 h,even surpassing the benchmark electrode couple composed of IrO2 and Pt/C.The present work may provide valuable insights for developing MOF-derived heterogeneous electrocatalysts with tailored interface/surface structure for widespread application in catalysis and other energyrelated areas.