A new approach is reported for tailoring the pore geometry in five series of multivariate metal-organic frameworks (MOFs) based on the structure [Zn2(bdc)2(dabco)] (bdc = 1,4-benzenedicarboxylate, dabco = 1,8-diazabicyclooctane), DMOF-1. A doping procedure has been adopted to form series of MOFs containing varying linker ratios. The series under investigation are [Zn2(bdc)2-x(bdc-Br)x(dabco)]·nDMF 1 (bdc-Br = 2-bromo-1,4-benzenedicarboxylate), [Zn2(bdc)2-x(bdc-I)x(dabco)]·nDMF 2 (bdc-I = 2-iodo-1,4-benzenedicarboxylate), [Zn2(bdc)2-x(bdc-NO2)x(dabco)]·nDMF 3 (bdc-NO2 = 2-nitro-1,4-benzenedicarboxylate), [Zn2(bdc)2-x(bdc-NH2)x(dabco)]·nDMF 4 (bdc-NH2 = 2-amino-1,4-benzenedicarboxylate) and [Zn2(bdc-Br)2-x(bdc-I)x(dabco)]·nDMF 5. Series 1-3 demonstrate a functionality-dependent pore geometry transition from the square, open pores of DMOF-1 to rhomboidal, narrow pores with increasing proportion of the 2-substituted bdc linker, with the rhomboidal-pore MOFs also showing a temperature-dependent phase change. In contrast, all members of series 4 and 5 have uniform pore geometries. In series 4 this is a square pore topology, whilst series 5 exhibits the rhomboidal pore form. Computational analyses reveal that the pore size and shape in systems 1 and 2 is altered through non-covalent interactions between the organic linkers within the framework, and that this can be controlled by the ligand functionality and ratio. This approach affords the potential to tailor pore geometry and shape within MOFs through judicious choice of ligand ratios.
Bibliographical noteFunding Information:
L.K.C. is funded by an EPSRC studentship. J.K.B. is funded by the EPRSC Doctoral Training Centre for Sustainable Chemical Technologies at the University of Bath (Grant No. EP/G03768X/ 1). D.T. was funded under ERC starting grant 277757. A.W. acknowledges support from the Royal Society and EPSRC Grant No. EP/K004956/1. The work benefits from the high performance computing facility at the University of Bath. Access to ARCHER supercomputer was facilitated through membership of the HPC materials Chemistry Consortium (EPSRC Grant No. EP/L000202). The authors thank Dr A. Otero de la Roza for useful discussions and Dr J. Lowe for NMR spectroscopic advice.
© The Royal Society of Chemistry 2016.
All Science Journal Classification (ASJC) codes
- Inorganic Chemistry