Regulating local charge distribution of single Ni sites in covalent organic frameworks for enhanced photocatalytic CO2 reduction

Abstract

Covalent organic frameworks (COFs) engineered by single-atom sites have attracted significant attention for CO2 photoreduction. However, precisely manipulating the chemical environment of active sites on the COFs is a grand challenge. Herein, we synthesized a series of isostructural COFs for photocatalytic CO2 reduction, where the strong coordination conformation guides atomically dispersed metal sites to chelate spontaneously in the predesigned imine-pyridine position of COFs. Experimental and theoretical results revealed the crucial influence of the single-Ni site engineering and electronic structures of COF configuration on improving extended π-conjugation, exciton dissociation, charge separation efficiency, and charge carrier migration. Benefiting from the synergistic effect, the optimal Ni-TAPT-COF exhibited a record-high CO production rate of 25.5 mmol g-1h-1 and a selectivity of 98.8%, even natural-sunlight-driven diluted CO2 (10%). This work paves the way for the rational design of high-performance COF-based photocatalysts at the molecular level, highlighting their practical potential for CO2 photoreduction.