Tailoring Morphology of MgO with Mg-MOF for the Enhanced Adsorption of Congo Red

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^-1 for MgO-M) and the secondary regeneration efficiency (over 96% removal rate across six cycles) offer promising prospects for future industrial applications, effectively addressing challenges related to poor water stability and difficult storability. Additionally, characterizations reveal the positive roles of alkaline sites, lattice oxygen, and pore structure in capturing significant quantities of CR through mechanisms such as electrostatic interactions, hydrogen bonding, and pore filling.