Ultrathin two-dimensional nanosheet metal-organic frameworks with high-density ligand active sites for advanced lithium-ion capacitors

Two-dimensional (2D) metal-organic frameworks (MOFs) exhibit great promise as high-energy anode materials for next-generation lithium-ion capacitors (LICs) due to their tunable chemistry and short ion transport paths. Nevertheless, high-throughput production of ultrathin 2D MOFs and energy storage mechanism analysis are still full of challenging. Here, theoretical calculations indicate that partial introduction of Fe in Co sites can enhance interaction of metal centers with water in solvents due to the strong 3d-2p orbital binding energy, which induces ultrathin nanosheets, resulting in exposure of high-density ligand active sites, lower band gap and higher Young modulus during lithium insertion. Greatly, ultrathin 2D Co/Fe-BDC nanosheets are obtained with a bottom-up method and can be scaled up to high-throughput production. In/ex-situ results further reveal highly reversible insertion/extraction reactions accompanied by crystalline to amorphous for Co/Fe-BDC anodes. LICs with optimal Co 4 Fe-BDC anode deliver high energy density (199.7 Wh kg -1 ) and power density (10000 W kg -1 ), together with superior cycle lifespan. This work offers in-depth insights for the high-throughput synthesis and the storage mechanism in 2D MOFs. A metal-organic framework with ultrathin two-dimensional nanosheet structures is fabricated by a simple bottom-up stirring method at room temperature and can be scaled up to high-throughput production. It exhibits enhanced lithium storage performance due to microstructure and element substitution, enabling the assembled lithium-ion capacitors to deliver high energy-power characteristic. • Ultrathin nanosheets metal-organic frameworks are manufactured by a room-temperature stirring method with the potential for scale-up production. • The DFT calculations reveal the introduction of Fe induces two-dimensional morphological growth and enhances electrochemical kinetics. • In/ex-situ results implicate Co/Fe-BDC anodes with high-density lithium storage sites for insertion/extraction accompanied by crystalline to amorphous. • The optimal LICs deliver high energy density (199.7 Wh kg -1 ) and power density (10000 W kg -1 ) as well as superior cycle lifespan.