A novel method to generate an aluminum-based MOF material named as MIL-121 was investigated. MIL-121, [Al(OH)(H2BTEC)·(H2O)]n is a prototypal aluminum MOF with 1,2,4,5-benzenetetracarboxylic acid (BTEC) linkers, which was normally produced by the hydrothermal method. Different from the hydrothermal method, the developed novel method does not involve high temperature and high pressure, instead the MOF material was produced by the traditional cooling crystallization method at ambient pressure and low temperature below 100 °C. The MIL-121 obtained by the novel method possesses the same lithium adsorption performance as that obtained by hydrothermal method, but with lower energy consumption and more environmentally friendly. Compared with hydrothermal method, this method has more advantage to be scaled up to industrialized production. The formation mechanism of MIL-121 in the novel method including nucleation and growth process of MOF crystal was studied. The results indicated that the size and morphology of MIL-121 crystals were influenced by the temperature and additives, respectively. As the reaction temperature increased to 100 °C, the operation time can be shortened to 2–5 h. The crystal habit that was predicted by Material studio software using BFDH, which is a model for crystal habit prediction proposed by Bravais, Friedel, Donnay, and Harker based on the crystal lattice parameters and crystal symmetry in the Morphology module, the simulated morphology of MIL-121 was in accord with that of the products obtained by cooling crystallization. The thermal stability of MIL-121 obtained by cooling crystallization is better than that obtained by the hydrothermal method.