Tetraphenylmethane-based Porous Organic Polymers: Synthesis And Selective Adsorption Of Gases

The separations of light hydrocarbons (C2H2, C2H4, C2H6, CH4) are very important industrial processes. The traditional separation technology is cryogenic distillation, which is very energy-intensive. Adsorptive separation is considered to be an energy-efficient technology for separations of these small gas molecules. Porous organic polymer, which is assembled by organic building blocks via covalent bonds, is good candidate for gas separations because of its high thermal stability, chemical and water stabilities, low density and free of metal. At present, the design and construction of POPs are mainly the connection of C-C and C-N, of which its synthetic methods are most in need of severe conditions, such as high temperature and pressure, aromatic solvents, inert atmosphere, precious metal catalyst, etc. In this thesis, tetrahedral tetraphenylmethane was used as the primitive material, and a series of tetrahedral building blocks, tetrakis(4-bromophenyl)methane, tetrakis(4-(9H-carbazol-9-yl)phenyl)methane and tetrakis-(4-aminophenyl)-methane were synthesized. Three simple and convenient reactions:acylation reaction in ice-water bath, solvent-free oxidative coupling reaction at room temperature, N-arylation reaction with Cu(acac)2 as catalyst, were used to achieve three amorphous porous organic polymers (POP-1, POP-2, POP-3) with high thermal stability and adsorptive selectivity for light hydrocarbons. POP-1 was polyamide porous organic polymer, synthesized with tetrakis-(4-aminophenyl)-methane and 1,3,5-benzenetricarbonyl trichloride by acylation reaction in ice-water bath. Solvent-free oxidative coupling of tetrakis(4-(9H-carbazol-9-yl)phenyl)methane achieved POP-2 via grinding at room temperature, with anhydrous ferric chloride as catalyst. A Cu(acac)2-catalyzed coupling reaction of tetrakis-(4-aminophenyl)-methane with tetrakis(4-bromophenyl)methane achieved POP-3. The POPs were characterized by FT-IR spectroscopy, X-ray powder diffraction, thermo-gravimetric analysis. We have investigated the permanent porosities and the uptakes of C2H2, C2H4, C2H6, CH4 and CO2 at 273 and 296 K of the POPs. To evaluate the C2/CH4 separation ability, the adsorption selectivities for C2H2, C2H4, C2H6 and CO2 over CH4 were calculated by Henry’s law based on the equation Sij=KH(i)/KH(CH4). Thermo-gravimetric analysis reveals POP-2 could stable up to 500℃. Gas adsorption measurement at 296 K indicate that POPs 1～3 as promising materials for highly selective separation of C2 hydrocarbons over CH4 at room temperature.