A facile eco-friendly hydrothermal route (180 degrees C, 12.0 h) has been developed for the first time to the uniform hierarchical porous MgBO2(OH) microspheres without the aid of any organic additive, surfactant or template, by using the abundant MgCl2 center dot 6H(2)O, H3BO3 and NaOH as the raw materials. The as-obtained porous microspheres exhibit a specific surface area of 94.752 mg.g(-1), pore volume of 0.814 cm(3).g(-1), and ca. 84.0% of which have a diameter of 2.25-3.40 mu m. The thermal decomposition of the porous MgBO2(OH) microspheres (650 degrees C, 2.5 degrees C.min(-1)L) leads to the porous Mg2B2O5 microspheres with well-retained morphology. When utilized as the adsorbents for the removal of CR from mimic waste water, the present porous MgBO2(OH) microspheres exhibit satisfactory adsorption capacity, with the maximum adsorption capacity q(m) of 309.1 mg.g(-1), much higher than that derived from most of the referenced adsorbents. This opens a new window for the facile green hydrothermal synthesis of the hierarchical porous MgBO2(OH) microspheres, and extends the potential application of the 3D hierarchical porous metal borates as high-efficiency adsorbents for organic dyes removal. (C) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.