Size- and morphology-controlled NH2-MIL-53(Al) prepared in DMF–water mixed solvents

We present here a simple solvothermal method to fabricate metal–organic framework NH2-MIL-53(Al) crystals with controllable size and morphology just by altering the ratio of water in the DMF–water mixed solvent system without the addition of any surfactants or capping agents. With increasing the volume ratio of water in the mixed solvents, a series of NH2-MIL-53(Al) crystals with different sizes and morphologies were synthesized. The average size of the smallest crystal is 76 ± 20 nm, which provides us a simple and environmentally friendly way to prepare nanoscale MOFs. The largest BET surface area of these samples is 1882 m2 g−1 that is mainly contributed by its micropore surface area, and its corresponding micropore volume is 0.83 cm3 g−1, which have greatly extended its application in the fields of gas adsorption and postsynthetic modification. All these samples were characterized by SEM, XRD, N2 adsorption/desorption, TGA and FT-IR. Then a mechanism for the impact of the water ratio on the crystal size and morphology is presented and discussed.