Tuning the Basicity/Nucleophilicity of Phenolate Anions Modulates Ion Pair Organocatalysis in the Reductive Functionalization of CO ₂

Reduction of CO 2 with amines and hydrosilane provides a diagonal approach to upcycling CO 2 to value‐added nitrogen‐containing chemicals. Ion pair organocatalysts composed of the tetrabutylammonium cation (TBA) and phenolate anions (X‐PhO) are designed to dictate the catalytic pathways of the reductive functionalization of CO 2 to formamide or N ‐methylamine under mild conditions. Two series of ion pair catalysts are evaluated by tuning the substituent effects and steric profile of the phenolate anions. For para ‐substituted phenolates (where X = NO 2 , H, CH 3 O, etc.), basicity/nucleophilicity modulate the turnover number (TON), identifying [TBA][4‐MeO‐PhO] as the optimal catalyst. Conversely, increasing steric hindrance in 2,6‐disubstituted phenolates leads to a significant decrease in TON compared to less‐hindered analogs. Mechanistic studies identify a steric‐dependent pathway: hindered phenolates activate silanes through phenyl carbonate intermediates, while unhindered ones proceed via direct activation. NMR and LC–MS analyses confirm the formation of silyl formate and the subsequent reduction to an aminal, identifying the latter as the key intermediate for the methylation pathway. The optimal catalyst converts 20 amines to formamides (0.5 MPa CO 2 , 25 °C) and 15 amines to N ‐methylated products (0.1 MPa CO 2 , 60 °C) in up to 99% yield, demonstrating that product selectivity is effectively governed by temperature and CO 2 pressure.