The surface area and structure of adsorbents are crucially important to its adsorption capacity. Herein, we focused on the correlation between the structures of 2D/3D materials and its adsorption properties by taking three kinds of cobalt aluminum layered double hydroxide (CoAl-LDH) as adsorbents, including a 3D hierarchical flower-like hollow/solid sphere (FH/FS-CoAl) and 2D plate (P-CoAl). As expected, FH-CoAl showed the highest adsorption capacity (similar to 2189.23 mg/g) for methyl orange (MO), benefiting from the highly accessible surface areas and more active sites of unique hollow structural characteristics inherited from the hierarchical flower-like hollow structures. Interestingly, compared with FS/FH-CoAl, P-CoAl exhibited the highest adsorption capacity enhancement times after being normalized with surface area, but displayed an inferior maximum adsorption capacity. The reasons could be mainly ascribed to (1) P-CoAl with 2D plate structures possessed more fully exposed active sites than FH-CoAl and (2) the compact and thick shell structure of the hollow structure made dye difficult to diffuse into the hollow interior. Moreover, the characterization analysis further confirmed that the electrostatic interaction, hydrogen bonding, and ion exchange were the main adsorption mechanisms for FH-CoAl and FS-CoAl, while electrostatic interaction was mainly an adsorption mechanism for P-CoAl. A deep understanding of synergistic modulation of surface area and structure effects of 2D/3D adsorbents will provide the opportunity for further enhancing the adsorption activity and offer a new pathway for design and optimization of advanced adsorbents in the near future.