Solution-Processable Naphthalene Diimide-Based Conjugated Polymers as Organocatalysts for Photocatalytic CO2 Reaction with Extremely Stable Catalytic Activity for Over 330 Hours

摘要

Nowadays, the photochemical conversion of CO2 to high-valueproducts is attracting tremendous research interest. Developing artificialphotocatalysts with excellent catalytic activity and long-term stability is still achallenge. This work demonstrates that solution-processable naphthalenedimide(NDI)-based conjugated polymers, PNDI-BT, PNDI-DTBT, and PNDI-BP, whichare copolymerization products of NDI with bithiophene (BT), 4,7-di(thiophen-2-yl)benzocl,2,5thiadiazole (DTBT), and biphenyl (BP), respectively, werecapable of catalyzing the photochemical reduction of CO2 to produce CO in thepresence of water without the need for metal-containing co-catalysts or sacrificialagents. In particular, the PNDI-BP-catalyzed reaction generated CH4 as well asCO. Results from time-resolved photoluminescence, photovoltage decay, electrochemical impedance spectroscopy, and transientphotocurrent response experiments indicate that PNDI-BP with the largest dihedral angles along the conjugated backbone possessedthe longest electron lifetime, the lowest charge-carrier recombination rate, and the smallest interfacial charge transfer resistance.Consequently, it had the best catalytic performance. Notably, PNDI-BP exhibited excellent recyclability, robust structural stability,and extremely steady catalytic activity for more than 330 h during a photocatalytic CO2 reaction. Furthermore, the solution-processability of the linear polymer allows the incorporation of porous substrates, which improve the reaction interface. The catalystsystem of PNDI-BP@molecular sieves with H2O/triethylamine doubled the CO yield to 214.8 μmol-g_(cat)~(-1) and enhanced the CH4yield by ~36 times to 61.4 μmol-g_(cat)~(-1) in an 18 h reaction.