Herein, we have developed a facile process of synthesizing N and O surface-terminated 2D molybdenum carbide nanomeshes (Mo2CTx NMs) and assembling them into 3D microflowers (Mo2CTx MFs) by one-step pyrolysis of Mo/Zn bimetallic imidazolate frameworks. When used as an oxygen evolution reaction (OER) catalyst, the Mo2CTx NMs thus derived exhibit outstanding catalytic activity with an overpotential of 180 mV at the current density of 10 mA cm(-2). This enables Mo2CTx NMs to become one of the best OER electrocatalysts ever reported, with the desired stability in alkaline environment which is a major challenge for most of the non-oxide/hydroxide based electrocatalyts. Additionally, the Mo2CTx MFs can catalyze the hydrogen evolution reaction (HER) and act as bifunctional electrocatalysts for overall water splitting which can attain a current density of 10 mA cm(-2) at 1.7 V. Mo LIII-edge X-ray near-edge absorption studies combined with theoretical calculations imply that surface-terminated oxygen is crucial in activating the outstanding OER performance, whereas the top Mo atomic sites on the surface contribute to excellent HER performance.