The Origin of the Reproduction of Different Nitrogen Uptakes in Covalent Organic Frameworks (COFs).

In order to quantitatively examine the activation level for covalent-organic frameworks (COFs) on gas adsorption, the effect of impurities on nitrogen uptakes in a series of boron-based COFs was investigated by grand canonical Monte Carlo simulation (GCMC), based on accurate force fields derived from high-level B2PLYP-D3/def2-TZVPP calculation. The conformations and the type of impurities were found to have little effect on the gas uptakes, but the quantity of impurities plays a crucial role on N2 loadings. More important, the terms of "activation mass ratio" and "activation volume ratio" were defined to estimate the realistic pore volume ratio for DBA-COFs (DBA=π-conjugated dehydro-benzoannulene), and predict the potential of gas uptakes in DBA-COFs. Our approach for DBA-COFs materials could also be adopted for high-throughput screening of a much vaster number of porous materials, to evaluate their impurities content and predict their adsorption potential.