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Water sorption cycle measurements on functionalized MIL-101Cr for heat transformation application
The water loading capacity and water cycle stability (40 adsorption/desorption cycles) of four nitro- or amino-functionalized MIL-101Cr materials (1-4) is assessed for heat transformation applications. Amino- or nitro-functionalized (1, 3) and partially amino- or nitro-functionalized MIL-101Cr (2, 4) have been synthesized through time-controlled postsynthetic modification of MIL-101Cr. The partially ffinctionalized materials (2, 4) contain about 78 mol 96 amino- or nitro-functionalized terephthalate linker. Hydrophilic nitro or amino functionalities were introduced into MIL-101Cr in order to achieve water loading at lower p/p(0) values for possible use in thermally driven adsorption chillers or heat pumps. Among the four materials studied, fully aminated MIL-101Cr-NH2, 1, and partially aminated MIL-101Cr-pNH(2), 2, showed the best water loadings (about 1.0 gH(2)O/gMIL) as well as water stability over 40 adsorption-desorption cycles. After 40 cycles, the X-ray powder diffractogram and Brunauer-Emmett-Teller (BET) surface determination of amino-functionalized materials indicated structural integrity with Delta(BET) = -6.3% after 40 cycles, while the nitro-functionalized MIL-101Cr exhibited a decrease in their BET surface of Delta(BET) = -25% and -20% for 3 and 4, respectively.