Reaction Site Designation by Intramolecular Electric Field in Troger's-Base-Derived Conjugated Microporous Polymer for Near-Unity Selectivity of CO2 Photoconversion

To facilitate solar-driven overall CO2 and H2O convsersion into fuels and O-2, a series of covalent microporous polymers derived from Troger's base are synthesized featuring flexural backbone and unusual charge-transfer properties. The incorporation of rigid structural twist Troger's base unit grants the polymers enhanced microporosity and CO2 adsorption/activation capacity. Density function theory calculations and photo-electrochemical analyses reveal that an electric dipole moment (from negative to positive) directed to the Troger's base unit is formed across two obliquely opposed molecular fragments and induces an intramolecular electric field. The Troger's base unit located at folding point becomes an electron trap to attract photogenerated electrons in the molecular network, which brings about suppression of carrier recombination and designates the reaction site in synergy with the conjugated network. In response to the discrepancy in reaction pathways across the reaction sites, the product allocation in the catalytic reaction is thereby regulated. Optimally, CMP-nTB achieves the highest photocatalytic CO production of 163.53 mu mol g(-1) h(-1) with approximately unity selectivity, along with H2O oxidation to O-2 in the absence of any photosensitizer or co-catalyst. This work provides new insight for developing specialized artificial organic photocatalysts.