The modulator driven polymorphism of Zr(IV) based metal-organic frameworks

The reaction of ZrCl4 and 2,5-thiophenedicarboxylic acid (H(2)tdc) in the presence of trifluoroacetic acid (Htfa) as modulator results in the formation of the new metal-organic framework (MOF) named DUT-126 (DUT = Dresden University of Technology). The nature and concentration of modulators are found to be decisive synthetic parameters affecting the topology of the formed product. DUT-126 (hbr) extends the series of polymorphs differing in topology, namely DUT-67 (reo), DUT-68 (bon) and DUT-69 (bct) to four, where DUT-67 and DUT-68 show the same eight-connected secondary building units as in DUT-126. In DUT-126, linker molecules have a peculiar orientation, resulting in hbr topology, which is described for the first time in this work for MOFs. DUT-126 contains three pore types, including two micropores surrounding mesoporous channels. DUT-126 is stable against hydrolysis and features permanent porosity with a specific surface area of 1297 m(2) g(-1) and a total pore volume of 0.48 cm(3) g(-1), calculated from the nitrogen physisorption isotherm measured at 77 K. This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.