Open Access

Four bisphosphinic acids RR´C[P(CH3)(O)OH]2 are characterized by 1H, 13Cf1Hg, and 31P{1H} NMR data. H3C-P-C-P-CH3 skeletons give rise to [A3X]2 spin systems. Some algebraic equations are derived for manual analysis of [A3X]2 spectra. HR NMR data for heteroaromatic substituents R in RC(H)[P(CH3)(O)OH]2 are reported. Dissociation constants and ion-specific chemical shifts dP of CH3C(OH)[P(CH3)(O)OH]2 are determined by 31P{1H} NMR controlled titrations of 2a.

: A catalyst-free Schiff base reaction was applied to synthesize two imine-linked covalent organic frameworks (COFs). The condensation reaction of 1,3,5-tris-(4-aminophenyl)triazine (TAPT) with 4,40-biphenyldicarboxaldehyde led to the structure of HHU-COF-1 (HHU = Heinrich-Heine University). The fluorinated analog HHU-COF-2 was obtained with 2,20,3,30,5,50,6,60-octafluoro 4,40 -biphenyldicarboxaldehyde. Solid-state NMR, infrared spectroscopy, X-ray photoelectron spectroscopy, and elemental analysis confirmed the successful formation of the two network structures. The crystalline materials are characterized by high Brunauer–Emmett–Teller surface areas of 2352 m2/g for HHU-COF-1 and 1356 m2/g for HHU-COF-2. The products of a larger-scale synthesis were applied to prepare mixed-matrix membranes (MMMs) with the polymer Matrimid. CO2/CH4 permeation tests revealed a moderate increase in CO2 permeability at constant selectivity for HHU-COF-1 as a dispersed phase, whereas application of the fluorinated COF led to a CO2/CH4 selectivity increase from 42 for the pure Matrimid membrane to 51 for 8 wt% of HHU-COF-2 and a permeability increase from 6.8 to 13.0 Barrer for the 24 wt% MMM