Unblocked intramolecular charge transfer for enhanced CO2 photoreduction enabled by an imidazolium-based ionic conjugated microporous polymer

Efficient solar energy-driven conversion of CO2 to valuable chemicals is challenging. Here we design an imidazolium-based ionic conjugated microporous polymer (ImI-CMP), which unblocks readily intramolecular charge transfer and triggers CO2 photoreduction. Under visible light irradiation, ImI-CMP incorporated with Co (II) species exhibits a high CO production rate of 2953 μmol g−1 h−1 and a turnover frequency of 30.8 h−1; these numbers are competitive to that of the best porous organic polymers. The mechanism studies reveal that two factors play key roles in the outstanding photocatalytic performance. First, the imidazolium motifs on the ImI-CMP enhance the activation of CO2. Second, π-conjugation structure and the built-in electric field allow ultrafast intramolecular photoinduced electron transfer in the ImI-CMP. This work provides a new strategy for designing high-performance organic photocatalysts for CO2 reduction by combining cationic imidazolium motifs and π-conjugation structures. Here we report an imidazolium-based ionic conjugated microporous polymer, which shows excellent CO2 photoreduction performance under visible light irradiation. Mechanism study revealed that the imidazolium motifs in it enhance the activation of CO2. Moreover, π-conjugation and the built-in electric field allow ultrafast intramolecular photoinduced electron transfer in the catalyst. [Display omitted] •Imidazolium-based ionic conjugated microporous polymer is designed.•The polymer exhibits extraordinary activity for photocatalytic CO2 reduction.•The imidazolium motifs offer a microenvironment for CO2 enrichment and activation.•Built-in electric field facilitates intramolecular electron transfer.