2D Porous Polymers with sp2-Carbon Connections and Sole sp2-Carbon Skeletons

2D porous polymers with a planar architecture and high specific surface area have significant applications potential, such as for photocatalysis, electrochemical catalysis, gas storage and separation, and sensing. Such 2D porous polymers have generally been classified as 2D metal-organic frameworks, 2D covalent organic frameworks, graphitic carbon nitride, graphdiyne, and sandwich-like porous polymer nanosheets. Among these, 2D porous polymers with sp(2)-hybridized carbon (Csp2) bonding are an emerging field of interest. Compared with 2D porous polymers linked by B-O, C(sic)N, or C(sic)C bonds, Csp2-linked 2D porous polymers exhibit extended electron delocalization resulting in unique optical/electrical properties, as well as high chemical/photostability and tunable electrochemical performance. Furthermore, such 2D porous polymers are one of the best precursors for the fabrication of 2D porous carbon materials and carbon skeletons with atomically dispersed transition-metal active sites. Herein, rational synthetic approaches for 2D porous polymers with Csp2 bonding are summarized. Their current practical photoelectric applications, including for gas separation, luminescent sensing and imaging, electrodes for batteries and supercapacitors, and photocatalysis are also discussed.