Two new metal-organic framework structures derived from terephthalate and linear trimetallic zinc building units

Two new zinc-terephthalate MOFs, (H2NEt2)[Zn-3(BDC)(3)(HCO2)]center dot 1.5DEF (1) and Zn-4(BDC)(3)(HCO2)(2)(DEF)(4) (2), based on trinuclear zinc secondary building units have been solvothermally synthesized from the well-studied MOF-5 system Zn-H2BDC-DEF (H2BDC = 1,4-benzenedicarboxylic acid or terephthalic acid; DEF = N,N-diethylformamide). It is shown that adding small amounts of formic acid to this system has a great influence on the formation of 3D networks based upon trimetallic zinc building units Zn-3(O2CR)(6). The structures of 1 and 2 comprise stacked 3(6) tessellated 2D zinc-terephthalate layers which are linked into 3D frameworks either by bridging formate monoanions (1) or by in situ generated neutral bridging units Zn(HCO2)(2)(DEF)(4) (2). Flowing supercritical-CO2 activation of 1 led to a partially (similar to 80%) desolvated and probably collapsed structure (1-SC) with a measured BET (Brunauer-Emmett-Teller) surface area of 38 m(2) g(-1). (C) 2014 Elsevier B.V. All rights reserved.