Multiscale study on ammonia adsorption by Li-Doped COF-10

Four types of Li-doped COF-10 have been designed and noted as COF-10-1Li, COF-10-2Li, COF-10-4Li, and COF10-6Li. COF-10 and COF-10-1Li have been used to adsorb both ammonia and hydrogen, and results indicate that incorporation of lithium brings about more enhancement for the adsorption of polar molecules. Ammonia adsorption on all the Li-doped COF-10 has been investigated. More lithium means higher adsorption capacity; however, the promotion of adsorption amounts is not proportional to the number of lithium atoms. Difference in adsorption capacities between COF-10-1Li and COF-10-2Li is slight. While six lithium atoms are included, a considerable promotion can be witnessed. The possible reason is that the positive potential shield on the surface of COF-10-6Li protects ammonia from repulsion from negative charges on the inner skeleton. These results suggest that not only charge amounts but also charge distribution have significant influence on adsorption behaviors.