Postsynthetic Lithium Modification of Covalent-Organic Polymers for Enhancing Hydrogen and Carbon Dioxide Storage

Recent experiment and simulation show that introduction of lithium in the frameworks can enhance the gas-storage capacities of framework materials. Here a covalent-organic polymer-1 (COP-1) has been synthesized through the self-polymerization of monomer 1,3,5-tris((4-bromophenyl)ethynyl) benzene (TBEB) by the nickel(0)-catalyzed Yamomoto reaction. To enhance gas adsorption properties of the COP-1 material, we have proposed a novel lithium-decorating approach in which the alkynyl functionalities in COP-1 are postsynthetically converted to lithium carboxylate groups with the aid of dry ultrapure CO2. In particular, the H2 uptake of lithium-modified COP material is 1.67 wt % at T = 77 K and ∼1 bar, which is increased by ∼70.4%, compared with the unmodified compounds. Besides, the enhancement effects of lithium modification on CO2 and CH4 adsorption have also been observed. It is expected that this approach proposed here would provide a new direction for lithium modification of MOFs and COFs for clean energy and environmental applications.