Ultrathin, Cationic Covalent Organic Nanosheets for Enhanced CO<sub>2</sub> Electroreduction to Methanol
Yun Mi Song, Peng Guo, Tinghao Ma, Jianjun Su, Libei Huang, Weihua Guo, Yong Liu, Geng Li, Yinger Xin, Qiang Zhang, Siwei Zhang, Hanchen Shen, Xing Feng, Deng‐Tao Yang, Jia Tian, Sai Kishore Ravi, Ben Zhong Tang, Ruquan Ye
Abstract
Abstract Metalloporphyrins and metallophthalocyanines emerge as popular building blocks to develop covalent organic nanosheets (CONs) for CO 2 reduction reaction (CO 2 RR). However, existing CONs predominantly yield CO, posing a challenge in achieving efficient methanol production through multielectron reduction. Here, ultrathin, cationic, and cobalt‐phthalocyanine‐based CONs (iminium‐CONs) are reported for electrochemical CO 2 ‐to‐CH 3 OH conversion. The integration of quaternary iminium groups enables the formation of ultrathin morphology with uniformly anchored cobalt active sites, which are pivotal for facilitating rapid multielectron transfer. Moreover, the cationic iminium‐CONs exhibit a lower activity for hydrogen evolution side reaction. Consequently, iminium‐CONs manifest significantly enhanced selectivity for methanol production, as evidenced by a remarkable 711% and 270% improvement in methanol partial current density ( j CH3OH ) compared to pristine CoTAPc and neutral imine‐CONs, respectively. Under optimized conditions, iminium‐CONs deliver a high j CH3OH of 91.7 mA cm −2 at −0.78 V in a flow cell. Further, iminium‐CONs achieve a global methanol Faradaic efficiency (FE CH3OH ) of 54% in a tandem device. Thanks to the single‐site feature, the methanol is produced without the concurrent generation of other liquid byproducts. This work underscores the potential of cationic covalent organic nanosheets as a compelling platform for electrochemical six‐electron reduction of CO 2 to methanol.