Accurate Layer Spacing Matching of Polyoxometalate (POM) Anion‐based Ionic Liquids (ILs) to Promote PET Alcoholysis

Abstract

AbstractMatching the active site of the catalyst with the carbonyl reactive site of PET at the nanoscale and achieve precise shearing of the PET reactive site at the molecular level by accurately modulating the catalyst layer spacing is particularly challenging. Herein, a new design strategy for green catalysts is proposed to synthesize a novel class of Polyoxometalate (POM) anion‐based ILs (POM‐ILs) [X]n[WZn3(H2O)2(ZnW9O34)2] (X=PyPs, Py, MIMPs, TEAPs, n=3, 6, 9, 12) with high thermally stable and adjustable layer spacing (1.00–1.63 nm). By adjusting the ratio of organic cations to match the spacing (1.34 nm) between the active sites of the catalyst with the spacing (1.32 nm) of the carbonyl functional groups on both sides of the PET benzene ring, the long PET chains were precisely sheared and rapidly degraded to bis(hydroxyethyl) terephthalate (BHET) in short time with the synergistic catalytic effect of anions and cations. Under the optimal conditions, the catalyst dosage was only 0.8 % of PET mass, and it could degrade 100 % in 30 min with BHET yield up to 85.35 %, and the yield of BHET was still greater than 85 % after 5 cycles. In addition, a possible mechanism of synergistic catalytic PET alcoholysis was proposed by density functional theoretical calculation. Moreover, the strategy of promoting PET alcoholysis by accurately modulating the spacing of the catalytic active site has not been reported.