Efficient and Selective Chemical Recycling of CO₂‐Based Alicyclic Polycarbonates via Catalytic Pyrolysis

Abstract

Chemical recycling of polymers to their constituent monomers is the foremost challenge in building a sustainable circular plastics economy. Here, we report a strategy for highly efficient depolymerization of various CO 2 -based alicyclic polycarbonates to epoxide monomers in solvent-free conditions by a simple Cr III -Salen complex mediated catalytic pyrolysis process. The chemical recycling of the widely studied poly(cyclohexene carbonate) exhibits excellent reactivity (TOF up to 3000 h À 1 , 0.1 mol % catalyst loading) and high epoxide monomer selectivity (> 99 %). Mechanistic investigation reveals that the process proceeds in a sequential fashion via a trans-carbonate intermediate.

CO2 Deprotection-Mediated Switchable Polymerization for Precise Construction of Block Copolymers

“…When performed at the relative low temperature T 1 , the PPNCl-catalyzed ring-opening copolymerization (ROCOP 1) of epoxide/PA exclusively gave the propagating block 1 (B 1 – ). After the consumption of epoxide, elevating the temperature to T 2 would trigger the deprotection of cyclic carbonate into epoxide accompanied by decarboxylation, which was carefully discussed in our recent work and other important literature . Then, B 1 – initiated ROCOP 2 of in situ released epoxide/PA proceeded to form the second block.…”

“…After the consumption of epoxide, elevating the temperature to T 2 would trigger the deprotection of cyclic carbonate into epoxide accompanied by decarboxylation, which was carefully discussed in our recent work 58 and other important literature. 60 Then, B 1 − initiated ROCOP 2 of in situ released epoxide/PA proceeded to form the second block.…”

Recent Advances in Monomer Design for Recyclable Polymers

“…Zn-3 与水分子形成的多核化合 物(Zn-3•xH 2 O) n 降解上述所得的聚碳酸环己烯酯回到环 氧环己烷的选择性高达 99% (图 12). 最近, 刘野和吕小 兵等 [113] 应用商品化的金属席夫碱 Cr III -Salen 和季铵盐 为催化剂, 在 140～200 ℃, 催化剂负载为 0.1 mol%的 条件下, 实现了聚碳酸环己烯酯定量解聚为环氧环己烷…”

Scale Synthesis of Poly(butylene carbonate-co-terephthalate) and Its Depolymerization–Repolymerization Recycling Process

“…Yu et al reported a highly efficient depolymerization method for recycling CO 2 -based alicyclic polycarbonates to the raw materials by a simple Cr III –Salen complex-mediated catalytic pyrolysis process. The chemical recycling method was able to recycle pure epoxide monomers without a complicated purification process . Based on the above-mentioned analysis, the chemical recycling of polycarbonates generally requires the presence of efficient catalysts and suitable solvents to facilitate the depolymerization process, which will have residual metal in the recycling monomer, restricting repolymerization, and the depolymerization solvents also easily created secondary pollution.…”