Gas sorption and selectivity study of N,N,N′,N′-tetraphenyl-1,4-phenylenediamine based microporous hyper-crosslinked polymers

Abstract

One of the most important parameters to design porous polymeric materials for gas storage and separation is to discover appropriate linker. Determining the effect of linker, in fixed core, over the selectivity and adsorption has been great challenge. Here, three different N,N,N′,N′-tetraphenyl-1,4-phenylenediamines (TPPA) based microporous hyper-crosslinked polymers synthesized by the Friedel-Craft reactions. Hypercrosslinked polymer, TPPA-DMM, was obtained from dimethoxymethane (DMM) and hypercrosslinked-covalent polymer, TPPA-DMB, from dimethoxybenzene (DMB) in presence of FeCl3. TPPA-CC, covalent triazine polymer was synthesized from cyanuric chloride (CC) via AlCl3 as the catalyst. After the careful characterization of these microporous structures with different analytical and spectral analyses, the gas uptake (for CO2, CH4, O2, CO, and H2) and selectivity properties (for CO2/N2, CO2/O2, for CO2/CO and CO2/CH4) were comparatively investigated at pipe gas temperatures and up to 1 bar. The high BET specific surface areas ranging from 742 to 883 m2/g with ultramicropore characters (0.53–0.58 nm), high chemical stability in different solvents even in concentrated acid and thermal stability (up to 450 °C) promised that these materials can be used in pipe gas processes. By changing the linkers on the core, materials have high gas uptake properties reaching 12.98 wt% for CO2 uptake, 1.57 wt% for CH4 uptake, 1.06 wt% for CO uptake at 1 bar/273 K and also reaching 1.28 wt% for H2 uptake at 1 bar/77 K. In addition, the unusual N2 phobic character down to 0.2 wt% and O2 phobic character down to 0.3 wt% were observed. The selectivity was calculated by using the ideal adsorbed solution theory (IAST). The selectivities were found reaching 80.4 for CO2/N2, 8.5 for CO2/CH4, 30.1 for CO2/CO and 39.1 for CO2/O2. These calculations show that the obtained polymers can be used in post combustion processes which needs high pressures and temperatures. The selectivities of the synthesized materials for the gas sorptions changed drastically by switching the linkers in all three materials. Interestingly, IAST calculations from single to dual gas, in the different ratios, showed that selectivities were almost the same for each polymer within itself at same temperature. To date, these are the first reported discoveries for the porous organic polymers in the literature.