In the past decade, adsorption method has attracted great attention on the lithium extraction. The key issue in adsorption technology is to develop adsorbents with high adsorption capacity, selectivity, and recycle-stability. Here, the highly efficient metal–organic framework adsorbents were developed for lithium extraction, which were fabricated by the in-situ conversion of MIL-121 in alkali solution. The adsorbent after acid activation, termed as H-CAOMIL, was featured with the hierarchical porosity, enhanced density of free carboxylic groups, and exposed aluminum-oxygen defect sites to enhance the ion transport and provide dual strong interaction for Li+. H-CAOMIL exhibited the remarkable Li+ adsorption capacity (QLi+ = 5.28 mg/g) and selectivity (αKLi = 21.33, αNaLi=9) from low-concentration lithium-containing solutions. Moreover, the H-CAOMIL can be easily regenerated in weakly acidic solution. Impressively, Li+ adsorption capacity retained at 92 % of the initial capacity even after five adsorption–desorption cycles. Furthermore, the comprehensive characterizations and theoretical calculations indicated that the specific coordination of COO-Li and AlO-Li played a crucial role in the recovery capacity and selectivity of Li+. This work offers precious insights for the future exploration of highly efficient adsorbents for lithium extraction.