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Electrochemical water splitting is considered a green and sustainable method of producing hydrogen energy. Herein, to pursue a highly efficient hydrogen evolution reaction, we fabricated high-performance electrocatalysts, by utilizing a bimetallic (Cu and Co) metal–organic framework to modify rGO through a one-step in situ approach. The synthesized CuCoOC@rGO presents a highly ordered structure with a defect-rich porous surface for the hydrogen evolution reaction (HER). Specifically, the appropriate adjustment of metal (Cu and Co), 1,3,5-benzenetricarboxylic acid (H3BTC), and rGO ratios leads to a well-defined morphology, which creates a defect-rich porous surface. Characterized by XRD, SEM, EDS, FT-IR spectroscopy, Raman spectroscopy, XPS, and BET, the morphology exposes more active sites, strong evidence for the promotion of electrocatalytic efficiency. Upon the analysis of the experimental data, the obtained CuCoOC@rGO catalyst exhibits excellent activity in alkaline media with a low overpotential of 120 mV at a current density of 10 mA cm−2, and a Tafel slope of 124 mV dec−1 for the hydrogen evolution reaction (HER). Guided by the structure–activity relationship, the superior HER activity of CuCoOC@rGO in alkaline electrolyte could originate from many sources, including: (1) as a self-supported substrate, CuCoOC@rGO not only leads to profitable electrical contact and mechanical stability but also firmly roots into the rGO without extra binders. (2) The highly ordered structure provides smooth ion and electron transport channels, which are conducive to electrolyte infiltration and gas release. (3) The abundance of defective pores on the surface of the nanoarrays, which offers more active sites for the catalytic process. This study provides new prospects for the rational design and fabrication of advanced hierarchical functional electrocatalysts for application in electrochemical energy devices. [ABSTRACT FROM AUTHOR]