The rational design of inexpensive and active electrocatalysts is crucial for upgrading chemicals from biomass. Here we report on highly efficient ternary NiCoMn-layered double hydroxide (NiCoMn-LDHs) nanosheets that are rich in oxygen vacancies and are produced under controllable conditions for the electro-oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA)) or Furfural to furonic acid (FurAc) under mild conditions. Electrochemical tests showed that the oxidation of HMF and furfural occurred prior to the oxidation of water at lower applied potentials with NiCoMn-LDHs catalysts. High yields of FDCA (91.7%) and FurAc (92.4%) were achieved in 2.5 h using 1.15 nm thick NiCoMn LDHs nanosheets under optimal conditions. The mechanism for superior performance, high durability, and good Faraday efficiency was elucidated through a comprehensive characterization, which confirmed that ultra-thin nanosheets exposed more Co-NiOOH active sites with oxygen vacancies, facilitating the synergistic effect between HMF and furfural oxidation reaction on Co– Ni and Mn2+ Conditions. The NiCoMn-LDHs nanosheet catalysts, which are rich in oxygen vacancies, represent a novel and energy-efficient solution for obtaining improved biochemicals.