Flexible Porous Organic Polymers with α,β-Enone-Linkage via AlCl₃-Catalyzed Horner–Wadsworth–Emmons Polymerization for Pd Recovery

In this work, highly porous organic polymers with α,β-enone-linkage were synthesized via the Horner–Wadsworth–Emmons (H-W-E) polymerization in 10–20 g, and the catalytic amount of AlCl₃ was found to increase the BET surface area of the as-prepared BIT-POP-120 and BIT-POP-121 dramatically (up to 716 m² g^–1), much higher than that of enone-liked porous organic polymers (POPs) reported. More importantly, this H-W-E polymerization of triphsophonate 4 with 2,5-hexanedione 6 provided a powerful way to offer 18% flexible moiety in BIT-POP-121 based on low-field NMR. Very high Pd/Pt selectivity of 3.54 and 28 was observed for BIT-POP-121 respectively, based on the adsorption capacity and K_d value using a binary solution of Pd²⁺ and Pt²⁺. This is very promising for the Pd recovery from the spent automotive catalytic converters in the future. The powerful strategy for making flexible POPs by H–W-E polymerization using easily available and stable aliphatic diketones will lead the development of high-performance flexible POPs for broad applications including recovery of precious metals in the near future.