Spatial confinement of copper single atoms into covalent triazine-based frameworks for highly efficient and selective photocatalytic CO2 reduction

Abstract

Converting CO 2 into carbonaceous fuels via photocatalysis represents an appealing strategy to simultaneously alleviate the energy crisis and associated environmental problems, yet designing with high photoreduction activity catalysts remains a compelling challenge. Here, combining the merits of highly porous structure and maximum atomic efficiency, we rationally constructed covalent triazine-based frameworks (CTFs) anchoring copper single atoms (Cu-SA/CTF) photocatalysts for efficient CO 2 conversion. The Cu single atoms were visualized by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images and coordination structure of Cu-N-C 2 sites was revealed by extended X-ray absorption fine structure (EXAFS) analyses. The as-prepared Cu-SA/CTF photocatalysts exhibited superior photocatalytic CO 2 conversion to CH 4 performance associated with a high selectivity of 98.31%. Significantly, the introduction of Cu single atoms endowed the Cu-SA/CTF catalysts with increased CO 2 adsorption capacity, strengthened visible light responsive ability, and improved the photogenerated carriers separation efficiency, thus enhancing the photocatalytic activity. This work provides useful guidelines for designing robust visible light responsive photoreduction CO 2 catalysts on the atomic scale. covalent triazine-based frameworks, Cu single atoms, photocatalytic CO 2 reduction, visible light, selectivity

Metallic active-site engineering: a bridge between covalent triazine frameworks and high-performance catalysts

“…78 By implanting metal single atoms into CTFs, the process of intermediate evolution and conversion happens more smoothly and the energy barrier will decrease because of the electron transfer and orbital overlaps between the d electrons of metals and the molecular orbitals of substrates. 79–82 As a representative work, Liang's group applied triazine COF supported Pd single atoms (Pd 1 /trzn-COF) in CO oxidation and illustrated the detailed roles of Pd single atoms and the trzn-COF as well as the corporative catalysis based on their chemical interactions. 14 The d–π interactions between Pd d orbitals and π electron centers in the trzn-COF (including sp 2 phenyl C atoms and imine (CN linker) N and O atoms) with electronegativity were ensured.…”

Strategies to improve the photocatalytic performance of covalent triazine frameworks

“…Moreover, they can be anchored onto the surface of photocatalysts to effectively promote the separation of photogenerated electron–hole pairs. 188–191 However, single-atom catalysts tend to aggregate due to their high surface free energy, resulting in a decrease in catalytic activities. To address this issue, CTFs with nitrogen-rich properties have been applied to serve as a promising support to improve the dispersibility and stability of single-atom catalysts.…”

“…To address this issue, CTFs with nitrogen-rich properties have been applied to serve as a promising support to improve the dispersibility and stability of single-atom catalysts. In recent years, various kinds of single atoms (such as Pt, 188,192 Fe, 193 Ni, 194,195 Pd, 196 Ir, 197 Cu, 189,198 Co, 191,199 Ti, 200 and more) have been anchored on CTFs for various photocatalytic applications. For instance, by constructing CTFs with -N 3 sites, Pt single-atom catalysts have been loaded for photocatalytic N 2 fixation, achieving an ammonia production rate of up to 171.40 μmol g −1 h −1 .…”

“…Cu, 189 Co, 191,201 Ru 202 and Re 203 are of great interest due to their considerable catalytic activity in the photocatalytic CO 2 RR. As an example, Cu single atoms confined into CTF-1 effectively enhanced the visible light absorption and the CO 2 adsorption capacity of CTF-1, with a production selectivity of CH 4 over 98.31% in the photocatalytic CO 2 RR.…”

Advances and challenges in single-site catalysts towards electrochemical CO2 methanation

“…2). [35][36][37][38][39][46][47][48][49][50][51][52][53][54][55][56][57] We take for granted that isolated sites cannot achieve the *CO-CO coupling step so that the further reduction of *CO can proceed. The multi-electron transfer step can be pushed gradually through appropriate electronic structure optimizations.…”