Triphenylamine-based porous organic polymers: Synthesis and application for supporting phosphomolybdate to fabricate efficient olefin oxidation catalysts

Two kinds of triphenylamine-based porous organic polymers (POPS) were synthesized by FeCl3-triggered Friedel-Crafts polymerization of triphenylamine (TPA) and formaldehyde dimethylacetal (FDA) in the absence or presence of benzene (Ph), which are denoted as POP-I (without additional Ph) and POP-II (with additional Ph as linker), respectively. Various characterization results confirm the successful synthesis of TPA-based polymers with different bridged linkers and hierarchical pore structure. Phosphomolybdic acid (HPMA) and cobalt phosphomolybdate (CoPMA) were immobilized onto the POPs, to form phosphomolybdate (PMA) functionalized POPs catalysts, and their catalytic properties were investigated for the selective oxidation of olefins with H2O2. All the PMA functionalized POPs materials are catalytically active for the epoxidation/oxidation of olefins, while CoPMA/POP-II shows the highest activity, stability and recyclability. TPA-based POPs have distinctive electron-donating and transferring ability, which can be further tuned by introducing more bridged linkers of -Ph and-CH2 groups. Multi interactions between PMA and POPS supports could be built through the electronic and geometric effects exerted by the 3-D POPs supports on the PMA clusters. Moreover, the existence of Co cations may further strengthen the interactions between PMA and POPs supports by forming electrostatic or coordination interactions with the TPA ligands, thus resulting in the high stability of the CoPMA/POP-II against leaching of active species during the H2O2 mediated catalytic oxidation process. (C) 2017 Elsevier Inc. All rights reserved.