End-End Connection Pattern of Trinuclear-Triangular Copper Cluster for Construction of Two Metal–Organic Frameworks: Syntheses, Structures, Magnetic and Gas Adsorption Properties

Two metal–organic frameworks containing a geometrically spin-frustrated trinuclear-triangular copper cluster ([Cu3O]) have been successfully isolated, which are {[Cu4.5(μ3-OH)­(dmtrz)3­(m-bdc)2.5­(H2O)2­(CH3OH)­(DMF)]·DMF·5H2O}n (MAC-8) and {[Cu5(μ3-OH)­(dmtrz)3­(bdc)3­(H2O)4]·3H2O}n (MAC-9) (Hdmtrz = 3,5-dimethyl-1H-1,2,4-triazole, H2m-bdc = 1,3-benzene­dicarbox­ylic acid, H2bdc = 1,4-benzene­dicarbox­ylic acid, DMF = N′,N-dimethyl­formamide). Magnetic and gas adsorption studies revealed the successful combination of strong antiferromagnetic properties (Jav = −106.6 and −113.7 cm–1 for [Cu3O] in MAC-8 and MAC-9, respectively) and high surface areas (1058 m2/g for MAC-8 and 1242 m2/g for MAC-9) in both of the structures. Further structural studies revealed that the high surface areas could be ascribed to the unique two-dimensional hexagonal pattern of [Cu3(O)] clusters, in which the [Cu3(O)] clusters are connected to each other in an end-end fashion via mononuclear copper ions/paddle-wheel units.