Synthesis, structure determination, and hydrogen sorption studies of new metal-organic frameworks using triazole and naphthalenedicarboxylic acid

Two new metal-organic framework compounds were synthesized under solvothermal conditions using Zn2+ ion, 1,2,4-triazole (TRZ), and 1,4- and 2,6-naphthalenedicarboxylic acids (NDC): Zn-4(TRZ)(4)(1,4-NDC) (2)center dot 2DMF center dot 2H(2)O ( 1) and Zn-4(TRZ)(4)(2,6-NDC)(2)center dot 2DMF center dot 4H(2)O ( 2). Their crystal structures were characterized by single-crystal X-ray diffraction. Structure 1 crystallizes in the P2(1)/n space group with a = 13.609(2) angstrom, b = 27.181(5) angstrom, c = 13.617(3) angstrom, beta = 92.46(1)degrees, V = 5032.4(16) angstrom(3), and Z = 4. Structure 2 crystallizes in orthorhombic Pna2(1) space group with a = 30.978(6) angstrom, b = 12.620(3) angstrom, c = 13.339(3) angstrom, V = 5215(2) angstrom(3), and Z = 4. Both structures are analogues of the previously reported Zn-4(TRZ)(4)(1,4-BDC)(2)center dot 16H(2)O where the layers of Zn-triazole moieties are pillared by aromatic dicarboxylates to create 3-D open frameworks. Nitrogen sorption studies revealed that these structures have Brunaer-Emmett-Teller (BET) surface areas of 362.1-584.1 m(2)/g. Hydrogen sorption experiments showed they can store 0.84-1.09 wt % of H-2 at 77 K and 1 atm. Although they do not contain large pores or surface areas, they possess the hydrogen sorption capacities comparable to those of highly porous metal-organic frameworks.