Efficient Solar-Driven Electrocatalytic Halogen-Mediated Ethylene Oxidation in Seawater by Metallophthalocyanine-Based COFs.

The electrocatalytic strategy to convert ethylene (C2H4) into high value-added chemicals has great potential for C2H4 utilization. The halogen-mediated indirect electrocatalytic ethylene oxidation reactions (EOR) offer an attractive strategy for C2H4 conversion while still challenging. In this work, we rationally designed a series of highly crystalline and stable metallophthalocyanine covalent organic frameworks (COFs) for EORs. Among these COFs, NiPc-TABQ COF achieved maximum Faraday efficiency (FE) of 81.3% for 2-chloroethanol, and CoPc-TABQ COF demonstrated exceptional EOR activity with FE of 76.5% for 2-bromoethanol, which showed one of the best performances among previous reports. More importantly, this process was capable of being driven by solar energy through photovoltaic (PV) integration and natural seawater as electrolyte and source of chlorine thus achieved the efficient chlorine-mediated EOR. Furthermore, the yield ClCH2CH2OH and BrCH2CH2OH tandemly converted into higher value-added chemicals including ethylene glycol and ethylene carbonate, achieving conversion rate of 70% and 90%, respectively. Mechanistic insights were elucidated through in situ experimental analyses and density functional theory (DFT) calculations confirmed the halogen-mediated processes. This work firstly realized the efficient EOR by COFs, also achieved solar energy driven and seawater electrolyte based green electrocatalysis for the first time, demonstrating their great potential in sustainable chemistry.