Covalent-Organic Framework-Manipulated Multi-Reactant Activation Enables Polystyrene Electrodegradation in Tandem With Over-Oxidation Product Upgrading.

Abstract

Polystyrene (PS) waste is exceptionally difficult to chemically degrade under environmental conditions, and the high-value utilization of low-value C1 products generated during the process has never been achieved. Herein, we constructed a metalloporphyrin-anthracene sp2 covalent-organic framework (COF) electrocatalyst, TAPP-FeIII-An, which displays high structural stability and outstanding capability in activating O2 and multi-reactants. This enables it to effectively electro-degrade PS into high-value benzoyl products (yield, 23.2%, Mw residue 0.3%) and re-convert 20% of C1 products into high-value 1-formyl-1,2,3,4-tetrahydroquinoline (anticancer drug intermediate) with 9.4% yield, through a tandem quinoline carbonylation reaction. This breaks the traditional dilemma where PS degradation produces low-value byproducts that are difficult to re-utilize. Electrochemical experiments combined with theoretical calculations reveal that the valence tautomerism (FeII-FeIII-FeIV) of metal center and active An ligand endow TAPP-FeIII-An catalyst with the ability to activate O2 (generating 1O2, •O2 -, and •OH) and multi-reactants (PS and CO), thus enabling efficient PS electrodegradation (to benzoyl products) in tandem with low-value C1 products carbonylation (to anticancer drug intermediate). In this process, the generated C1 products (HCOOH, CO) were re-activated by TAPP-FeIII centers, and then react with 1,2,3,4-tetrahydroquinoline for high-value conversion. This work pioneers a tandem conversion strategy for PS waste degradation and low-value C1 products upgrading.