Synthesis, Structure Determination, and Hydrogen Sorption Studies of New Metal−Organic Frameworks Using Triazole and Naphthalenedicarboxylic Acid

Abstract

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): Zn4(TRZ)4(1,4-NDC)2·2DMF·2H2O (1) and Zn4(TRZ)4(2,6-NDC)2·2DMF·4H2O (2). Their crystal structures were characterized by single-crystal X-ray diffraction. Structure 1 crystallizes in the P21/n space group with a = 13.609(2) Å, b = 27.181(5) Å, c = 13.617(3) Å, β = 92.46(1) °, V = 5032.4(16) Å3, and Z = 4. Structure 2 crystallizes in orthorhombic Pna21 space group with a = 30.978(6) Å, b = 12.620(3) Å, c = 13.339(3) Å, V = 5215(2) Å3, and Z = 4. Both structures are analogues of the previously reported Zn4(TRZ)4(1,4-BDC)2·16H2O 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 m2/g. Hydrogen sorption experiments showed they can store 0.84−1.09 wt % of H2 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.