The active site is a highly anticipated property of adsorbent in the field of separation, as it enables a concurrent enhancement of both adsorption efficiency and adsorption rate. Herein, employing morphology-oriented regulation, we successfully fabricated heterogeneous MgO adsorbent from a magnesium-based metal-organic framework (MOF) precursor, octahedral MgO-M and laminated sheets MgO-P, for the capture of Congo red (CR). Specifically, the octahedron MgO-M exhibits a greater abundant of moderately and strongly alkaline sites, which facilitate the adsorption of CR. Furthermore, the synergistic effect between alkaline site and lattice oxygen further enhances the adsorption process. The adsorption data align more closely with the Pseudo-second-order kinetic model and Langmuir models. Notably, the exceptional adsorption capacity (exceeding 1900 mg·g
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