Multi-metal-variate covalent organic frameworks as redox mediators for indirect electrocatalytic S-S bond construction

Inspired by high-entropy materials, it is a worthwhile direction to develop multi-metal integrated catalysts to study their synergistic catalytic effects in catalysis field. However, achieving this in porous crystalline materials like covelent organic frameworks (COFs) for backend catalysis reactions remains scarce and challenging to date. Herein, a series of multi-metal-variate COFs (i.e., Quint-MMV-COF, Tetra-MMV-COF and Tri-n-MMV-COF (n = 1, 2 and 3)) have been prepared that can be applied in indirect electrocatalysis. These MMV-COFs with advantages of multi-metal sites, porous structures and appropriate work function can serve as solid-phase redox mediators for the catalytic production of liquid-phase S-S bond products and gas-phase H₂ product. Interestingly, the optimal Quint-MMV-COF presents excellent electrocatalytic efficiency for S-S bond products (yields up to 99%) and H₂ (~1.62 mmol·g^–1·h^–1) and can be readily recycled for 6 cycles. At the same time, 1.52 g product with a yield of ~92% can be obtained in the amplification reaction, showing much potential in industrial production. Validated by theoretical calculations, the synergistic effect of multi-metal sites can result in appropriate work function to boost the electron transfer and intermediate adsorption/conversion to achieve excellent overall S-S coupling efficiency.