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):  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) ų, 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) ų, 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.