Because of their nontoxicity, economic applicability, and excellent performance on adsorptive desulfurization, the fabrication of Cu(I) sites onto porous supports has drawn much attention. However, high temperatures (usually >= 700 degrees C) are required for the formation of Cu(I) sites from Cu(II) species through the traditional autoreduction method, which is unworkable for thermolabile metal organic frameworks (MOFs). Here, we report a strategy named vapor induced reduction (VIR) to convert Cu(II) species to Cu(I) in MIL-101(Cr), in which ethanol is used as an environmentally benign reductant. The entire formation of Cu(I) from Cu(II) with more than 96% selectivity is allowed, at a relatively low temperature of 200 degrees C, and well-maintains the structure of the MOF. Moreover, the generated Cu(I) sites exhibit good performances in adsorption desulfurization with regard to both activity and reusability.