AM：柱层状COFs--CO2RR

本文要点：

1. 全球对能源安全和气候变化的日益关注已经加强了开发电化学CO2还原(eCO2RR)的可持续策略的努力。共价有机框架(COFs)由于其可调结构、高表面积和丰富的活性中心而成为eCO2RR的有前途的电催化剂。然而，2D COFs的性能通常受到层堆叠的限制，这限制了活性位点的暴露并降低了选择性。

2. 为了克服这些挑战，开发了一种称为柱层COFs (PL-COFs)的新型COFs，其具有可调的层间间距和3D架构。使用PXRD、TEM、XPS和EIS的表征证实了柱分子的成功整合，这导致层间间距、结晶度和孔隙率的增加。这些结构上的进步导致显著提高了CO2到CO转化的电化学活性和选择性。

3. 密度泛函理论模拟表明，增强的CO2吸附和CO脱附是PL-COF-1优异性能的原因，它具有最大的层间距。这种材料实现了令人印象深刻的91.3%的法拉第效率，并表现出显著的电流密度，超过了最初的COF-366-Co和PL-COF-2。

4. 这些发现突出了柱化策略在优化COF基电催化剂中的有效性，为下一代用于CO2还原和可持续能源转化的材料铺平了道路。

Figure 1. Schematic representation of a) 2D COF-366-Co with ??–?? interactions, 3D PL-COFs with metal-ligand coordination bonds between Co(II) porphyrin and b) Pz, and c) Bp (only three layers and one pore are shown for clarity), and d) the pillaring strategy for designing 3D PL-COFs through metal-ligand coordination from 2D-layered COFs.

Figure 2. PXRD patterns of a) COF-366-Co, b) PL-COF-2, and c) PL-COF-1 based on AA slipped stacking models. d) PXRD patterns of PL-COF-2 synthesized using different equivalents of Pz (1.2 and 2.0 eq.) under Sc(OTf)3-catalyzed conditions. e) PXRD patterns of PL-COF-1 incorporating varying equivalents of Bp under Sc(OTf)3-catalyzed conditions. f) N2 adsorption–desorption isotherms and BET surface areas, and pore size distributions (grey dots and curve), pore volumes (red dots and curve), and optical images (inset) for g) COF-366-Co, h) PL-COF-2, and i) PL-COF-1.

Figure 3. a) HRTEM image and lattice spacing measurement of COF-366-Co; b) HRTEM image and lattice spacing measurement of PL-COF-2; c,d) HRTEM images and lattice spacing measurements of PL-COF-1. e) High-resolution XPS spectra of the N 1s for PL-COF-1, PL-COF-2, and COF-366- Co. f) High-resolution XPS spectra of the Co 2p for PL-COF-1, PL-COF-2, and COF-366-Co.

Figure 4. a) Linear sweep voltammetry (LSV) curves of COF-366-Co, PL-COF-2, and PL-COF-1 in CO2-saturated and Ar-saturated 0.1 m KHCO3 electrolyte at a scan rate of 5 mV s−1. b) Faradaic efficiency for CO production (FECO%) and CO partial current density from −0.50 to −1.00 V vs RHE for COF-366-Co, PL-COF-2 and PL-COF-1. c) Tafel plot for COF-366-Co, PL-COF-2, and PL-COF-1, illustrating the kinetics of CO production. d) Nyquist plots comparing the electrochemical impedance of COF-366-Co, PL-COF-2, and PL-COF-1. e) Stability test of PL-COF-1 showing total current density and FECO% for CO production at −0.70 V over a duration of 12 h. f) Comparative analysis of the optimal FECO% reported for porphyrin COF-based electrocatalysts in H-type electrochemical cells.

Figure 5. a) Mechanistic illustration of the eCO2RR process on PL-COF-2, PL-COF-1, and COF-366-Co. The upper box represents the catalytic center states, while the lower box shows the corresponding catalyst surface states. Gibbs free energy diagrams illustrating the b) ligand detachment (where L represents the ligand, i.e., Pz or Bp) and c) CO2-to-CO reduction pathway for PL-COF-2, PL-COF-1, and COF-366-Co. d) Energy requirements for the four key steps in the eCO2RR process for each catalyst. e) Charge density differences for CO adsorption on PL-COF-1, COF-366-Co, and PL-COF-2.

https://doi.org/10.1002/adma.202419547