Construction of Azo-Linked Covalent Organic Frameworks via Monomer Exchange for Enhanced Photocatalytic Performance

The structural uniqueness of covalent organic frameworks (COFs) has brought great potential for their applications in photocatalysis. Two novel azo-linked COFs AZO-B-COF and AZO-T-COF were successfully constructed by the monomer exchange method. Significantly, two as-synthesized azo COFs presented a much higher photodegradation rate of 96 % and 51 % for AZO-T-COF and AZO-B-COF, respectively, which was in sharp contrast to the almost 0 degradation rate of imine COFs. And as expected, AZO-T-COF could be cycled at least 5 runs without a significant decrease in catalytic efficiency. Systematical experiments and theoretical calculations showed that comparing with imine COFs, conjugated structure of azo COFs broadened the visible-light absorption range and improved the transfer efficiency of the photocarriers. The N-rich azo bonds acted as an electron acceptor and made the materials better planarity. This work not only enriches COFs family but also demonstrated the superiority of azo-linked COFs. Two azo-linked COFs AZO-B-COF and AZO-T-COF were successfully constructed by the monomer exchange method. Significantly, two as-synthesized azo COFs presented a much higher photodegradation rate of 96 % and 51 % for AZO-T-COF and AZO-B-COF, respectively, which was in sharp contrast to the almost 0 degradation rate of imine COFs. (COF means Covalent Organic Frameworks) image