Designing Local Electron Delocalization in 2D Covalent Organic Frameworks for Enhanced Sunlight-Driven Photocatalytic Activity

Abstract

Electron delocalization is a versatile method to tune the electronic structure of materials for maximizing their maximizing performances. Herein, TPBD covalent organic frameworks (COFs) with controlled electron-delocalization characteristics (denoted as TPBD-R-COF, R = H, F, CN, and NO2) were synthesized by molecular engineering to systematically investigate the effect of electron delocalization on photocatalytic performance. We found that the photocatalytic performance can be enhanced by modulating local electron delocalization in COFs. The photocatalytic activity of TPBD-CN-COF is more than 12 times greater than that of TPBD-H-COF in oxidative coupling of amines to imines, where the yield of product was increased from 8 to 99%. The experimental results and theoretical calculations revealed that TPBD-CN-COF with the optimal electron-attracting group of −CN shows the highest charge separation efficiency and electron transport rate, while excessive electron delocalization is not better for such properties. Our findings provide a strategy to design and optimize the photocatalytic performance of COF-based catalysts.

CuI-anchored porous covalent organic frameworks for highly efficient conversion of propargylic amines with CO2 from flue gas

“…Simultaneously, the stretching vibration of –CO in Tp (1639 cm −1 ) and –N–H in BD (3323 and 3199 cm −1 ) completely disappeared, indicating the successful condensation between the amino and aldehyde groups to form a β-ketoamine structure. 41 In contrast to TpBD-COF, the FT-IR spectrum of Cu I -TpBD-COF showed no significant changes (Fig. S1†), suggesting that Cu I was immobilized within TpBD-COF through interlayer interactions.…”

Progress of Covalent Organic Framework Photocatalysts: From Crystallinity–Stability Dilemma to Photocatalytic Performance Improvement

“…In heterogeneous photocatalysis, there exist common methodologies to enhance photocatalytic performance, including but not limited to enhancing light harvesting, accelerating charge separation, increasing active sites, and lowering reaction activation barriers. − As a polymeric semiconductor, COFs usually hold relatively lower dielectric constants and thus greater exciton binding energy, indicating that larger energy barriers for exciton dissociation should be overcome in comparison with inorganic photocatalyst counterparts. − Therefore, effective strategies facilitating exciton dissociation are vital for enhancing the photoactivity of COFs . The following section will discuss the most recent advances in improving the photocatalytic performance of the COFs.…”