Tuning of Microenvironment in Covalent Organic Framework via Fluorination Strategy promotes Selective CO Capture.

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF, respectively, to demonstrate their relative effect on CO adsorption capacity and also CO /N selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m  g , total pore volume 0.3647 ccg ), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m  g , total pore volume 0.2978 ccg ). This fact leads to an enormous decrease in the CO adsorption capacity and CO /N selectivity of TF-COF, though it shows stronger affinity towards CO with a Qst of 37.76 KJ/mol. The more CO adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF. Further, PD-COF exhibited CO /N selectivity of 16.8, higher than that of TF-COF (CO /N selectivity 13.4).