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

• Two new zinc-terephthalate MOFs based on trinuclear Zn SBU have been synthesized.
• These 3D MOFs have been synthesized from the MOF-5 system Zn–H2BDC–DEF.
• Addition of small amounts of formic acid has a great influence on their formation.
• Their structures comprise stacked 36 tessellated 2D zinc-terephthalate layers.
• The layers are linked by bridging formate monoanions or by Zn(HCO2)2(DEF)4 units.

Two new zinc-terephthalate MOFs, (H2NEt2)[Zn3(BDC)3(HCO2)]·1.5DEF (1) and Zn4(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 Zn3(O2CR)6. The structures of 1 and 2 comprise stacked 36 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 (∼80%) desolvated and probably collapsed structure (1-SC) with a measured BET (Brunauer–Emmett–Teller) surface area of 38 m2 g−1.

The structures of MOF 1 and 2 comprise stacked 36 tessellated 2D zinc-terephthalate layers. The layers are linked into 3D frameworks by bridging formate monoanions (1) or by neutral Zn(HCO2)2(DEF)4 units (2).Figure optionsDownload as PowerPoint slide