A metal–free porous organic polymer with high CO2 adsorption for robust aqueous CO2 photoreduction via molecular regulation

•A metal-free porous organic polymer has been prepared through molecular regulation.•The porous organic polymer has shown both high CO2 adsorption and robust CO2 photoreduction with high selectivity in water.•Detailed experiments through optical and photoelectrochemical measurements have been conducted to elucidate the mechanism. Development of photocatalysts with both high CO2 adsorption capacity and robust CO2 reduction performance is promising toward carbon capture and utilization (CCU). Herein, a porous organic polymer (POP) based on molecular monomers 1,2,3,5–Tetrakis(carbazol–9–yl)–4,6–dicyanobenzene (4CzIPN) and 9–(4–([2,2′:6′,2′'–terpyridin]–4′–yl)phenyl)–9H–carbazole (CzTPY) has been prepared for metal–free photocatalytic reduction of CO2 to CO with 94.7% selectivity in 100% aqueous medium. The POP displays a yield of CO up to 265.7 mmol g–1, which is among the highest yields for POPs–based photocatalytic systems. More importantly, the POP also shows a high CO2 uptake of 109.1 cm3 g–1 (21.4 wt%) at 273 K and 1 atm. External photosensitizers or catalysts are not required in this photocatalytic system. Mechanistic studies indicate the introduction of CzTPY improved the electron transfer and charge separation. These results show a feasible way to construct POP–based photocatalysts not only capturing CO2 efficiently but also catalyzing CO2 reduction with a high yield by rational regulation of molecular monomers. [Display omitted]