Fluorous Metal-Organic Frameworks and Nonporous Coordination Polymers as Low-kappa Dielectrics

A fluorous metal–organic framework [Cu(FBTB)(DMF)] (FMOF-3) [H2FBTB = 1,4-bis(1-H-tetrazol-5-yl)tetrafluorobenzene] and fluorous nonporous coordination polymer [Ag2(FBTB)] (FN-PCP-1) are synthesized and characterized as for their structural, thermal, and textural properties. Together with the corresponding nonfluorinated analogues lc-[Cu(BTB)(DMF)] and [Ag2(BTB)], and two known (super)hydrophobic MOFs, FMOF-1 and ZIF-8, they have been investigated as low-dielectric constant (low-κ) materials under dry and humid conditions. The results show that substitution of hydrogen with fluorine or fluoroalkyl groups on the organic linker imparts higher hydrophobicity and lower polarizability to the overall material. Pellets of FMOF-1, FMOF-3, and FN-PCP-1 exhibit κ values of 1.63(1), 2.44(3), and 2.57(3) at 2 × 10^6 Hz, respectively, under ambient con-ditions, versus 2.94(8) and 3.79(1) for lc-[Cu(BTB)(DMF)] and [Ag2(BTB)], respectively. Such low-κ values persist even upon exposure to almost satu-rated humidity levels. Correcting for the experimental pellet density, the intrinsic κ for FMOF-1 reaches the remarkably low value of 1.28, the lowest value known to date for a hydrophobic material.

A fluorous metal-organic framework [Cu(FBTB)(DMF)] (FMOF-3) [H2FBTB = 1,4-bis(1-H-tetrazol-5-yl)tetrafluorobenzene] and fluorous nonporous coordination polymer [Ag-2(FBTB)] (FN-PCP-1) are synthesized and characterized as for their structural, thermal, and textural properties. Together with the corresponding nonfluorinated analogues lc-[Cu(BTB)(DMF)] and [Ag-2(BTB)], and two known (super)hydrophobic MOFs, FMOF-1 and ZIF-8, they have been investigated as low-dielectric constant (low-kappa) materials under dry and humid conditions. The results show that substitution of hydrogen with fluorine or fluoroalkyl groups on the organic linker imparts higher hydrophobicity and lower polarizability to the overall material. Pellets of FMOF-1, FMOF-3, and FN-PCP-1 exhibit kappa values of 1.63(1), 2.44(3), and 2.57(3) at 2 x 10(6) Hz, respectively, under ambient conditions, versus 2.94(8) and 3.79(1) for lc-[Cu(BTB)(DMF)] and [Ag-2(BTB)], respectively. Such low-kappa values persist even upon exposure to almost saturated humidity levels. Correcting for the experimental pellet density, the intrinsic kappa for FMOF-1 reaches the remarkably low value of 1.28, the lowest value known to date for a hydrophobic material.