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A two-stage process has been developed for the pyrolysis of high-density polyethylene to obtain light olefins, where probable mechanisms for each stage pyrolysis were proposed in our previous study. This work aims to establish molecular-level kinetic models for the first-stage pyrolysis at a lower temperature and for the second-stage pyrolysis at a higher temperature, respectively, to predict the overall reaction performances in accordance to the role of detailed mechanisms. A structure-oriented lumping (SOL) method based molecular-level kinetic model can effectively describe the first-stage pyrolysis, while a detailed molecular-level kinetic model is developed for the second-stage pyrolysis to track the evolutions of all alkanes, olefins, and diolefins, with special focus on the formation of light olefins. The established separate models can achieve the automatic generation of complex reaction networks and present good agreement with experimental data obtained from the first- and second-stage. In addition, the first-stage model indicates that the random scission plays an important role in the pyrolysis process at lower temperatures, while the chain-end scission mechanism dominates the second-stage reaction to produce light olefins at higher temperatures. As a whole, the molecular-level modelling scheme behaves excellently at a wide range of temperature, which provides guidance for upgrading the pyrolysis process. • A molecular level kinetic model is established for the two-stage HDPE pyrolysis. • The reaction network is generated automatically and visualized. • This model achieves excellent agreement with experimental data. • The competition of two scissions and important role of temperature are quantified. [ABSTRACT FROM AUTHOR]

[Display omitted] • The I 2 nanotraps were used by introducing adjacent IBSs and LBSs on the skeleton. • The absorbent shows high I 2 uptake capacity (37 wt%) among all COF materials. • IBSs and LBSs synergistically promote iodine adsorption. Covalent organic frameworks have been recognized as promising porous materials for the radioactive iodine capture. However, most COFs often suffer from low adsorption capacity under practical conditions (typically ≥ 150 °C, ≤ 150 ppmv I 2) due to the lack of strong binding sites and low affinity toward iodine, which restricts their application in industrial relevant conditions. Here, we develop a strategy of constructing highly efficient I 2 nanotraps by manipulating two kinds of adsorption sites (ionic binding sites and Lewis binding sites) located at adjacent spatial positions, thereby realizing the synergistic binding toward I 2. The obtained I 2 nanotrap 4F-iCOF-TpBpy-I- delivers a remarkable I 2 uptake capacity of 37 wt% at 150 °C and 150 ppmv of I 2 , which illustrate a record-high value for all COFs reported so far. This work opens a new avenue for the rational design of COF materials toward highly efficient I 2 capture and related application. [ABSTRACT FROM AUTHOR]