本文要点：
局部电场(LEF)在催化过程中起重要作用；然而，活性位点周围电场微环境的精确构建和操纵仍然是一个重大挑战。
在这里，作者通过将主体大环18-冠-6 (18C6)引入到含钴酞菁(CoPc)的共价有机框架(COF)中，开发了一种实现LEF的超分子策略。
利用18C6和钾离子(K+)之间的超分子相互作用，可以在CoPc周围建立局部增强的K+浓度，以在催化活性Co位点周围产生LEF微环境。
具有这种超分子构建的LEF的COF在光催化CO2还原反应(CO2RR)中实现了高达7.79 mmol mmolCo–1h–1的活性，与没有18C6单元的同类产品相比，提高了180%。
通过改变具有不同抗衡离子的钾盐，充分利用K+@18C6相互作用，可以微妙地控制LEF的效应。
原位光谱和密度泛函理论计算表明，K+与18C6的络合产生了稳定CO2RR中涉及的关键中间体*COOH的正电场，这可以通过卤离子介导的K+@18C6相互作用和氢键相互作用来调节，从而导致不同程度的催化性能提高。
Scheme 1. Schematic Representation of the Synthesis of CoPc-TPA and CoPc-TPA-CE under Solvothermal Conditions
Figure 1. Structural and characterization of CoPc-TPA and CoPc-TPA-CE. Experimental PXRD of (a) CoPc-TPA and (d) CoPc-TPA-CE and simulated PXRD from models in the P4/MMM and I422 space groups, respectively. Top and side views of a graphical representation of (b and c) CoPc-TPA and (e and f) CoPc-TPA-CE with AA stacking, respectively (C, light gray; N, blue; O, red; H, white.). To visualize the arrangement of crown ethers in CoPc-TPA-CE, one of the two layers is marked with cyan. (g) SEM and (h) TEM (inset of h: locally enlarged TEM image) images of CoPc-TPA.
Figure 2. (a) Comparison of the FT-IR spectra of TPA, TPA-CE, CoTAPc, CoPc-TPA, and CoPc-TPA-CE. The Co K-edge EXAFS spectra of (b) CoPc-TPA, CoPc, and Co foil, and (c) CoPc-TPA-CE, CoPc, and Co foil. High-resolution Co 2p XPS spectra of (d) CoPc-TPA and (e) CoPcTPA-CE.
Figure 3. UV−vis-NIR spectra (inset: Tauc plot) and Mott−Schottky plots of (a, c) CoPc-TPA and (b, d) CoPc-TPA-CE.
Figure 4. Photocatalytic CO2RR performance of Ru(bpy)3Cl2, CoPcTPA, and CoPc-TPA-CE in the absence and presence of KF, KCl, KBr, or KI. To accurately evaluate the catalytic performance of the two materials, the activity values are normalized based on the equivalents of Co active sites.
Figure 5. Mechanistic investigation of the electric ffeld-regulated photocatalytic CO2RR. In situ DRIFTS of CO2RR catalyzed by (a) CoPc-TPA and (b) CoPc-TPA-CE under visible light irradiation. (c) Gibbs free energy diagrams for the reduction of CO2 to CO catalyzed by CoPc-TPA, CoPc-TPA-CE, and K+@CoPc-TPA-CE. Electrostatic potential diagrams of (d) CoPc-TPA-CE and (e) K+@CoPc-TPA-CE before and after the introduction of K+ (the color gradient from red to blue represents the potential change from negative to positive; isovalue: 0.05). (f) Gibbs free energy diagram after hydrogen bonding between counteranions K+@18C6 and *COOH.
https://doi.org/10.1021/jacs.4c16538
