The controlled preparation of two-dimensional (2D) nanosheets of metal–organic frameworks (MOFs), with tailorable methodologies, properties, and applications, is of significant importance. Here, in this work, by subtle control of the ultrasonic duration and solvent polarity, the iron(II)-based 2D MOF Fe(pyz)2Cl2 (pyz = pyrazine) has been elegantly tailored into 2D nanosheets (lateral size ≥500 nm in aqueous, with ultrasonic duration of 30 min) and one-dimensional (1D) nanoribbons (lateral size ≤100 nm in ethanol solution, with ultrasonic duration of 90 min). The aqueous suspension of 2D nanosheets was featured with thermal-induced spin-state transition at around room temperature and can be used as effective Fenton catalysts for degradation of water-soluble organic dyes, whereas the ethanol suspension of 1D nanoribbons can act as a versatile nanoplatform for trans-to-cis isomerization of 4, 4′-azopyridine. These results may provide a novel strategy for the controlled preparation of layered nanomaterials. •Custom-made morphologies of two-dimensional metal–organic framework nanosheets have been achieved.•Thermal-induced above room temperature spin-state transition has been observed.•Efficient Fenton catalysts have been demonstrated.•A versatile nanoplatform for trans–cis isomerization has been presented.