Engineering Single-Atom Active Sites on Covalent Organic Frameworks for Boosting CO₂ Photoreduction

Abstract

Solar carbon dioxide (CO 2 ) conversion is an emerging solution to meet the challenges of sustainable energy systems and environmental/climate concerns. However, the construction of isolated active sites not only influences catalytic activity but also limits the understanding of the structure−catalyst relationship of CO 2 reduction. Herein, we develop a universal synthetic protocol to fabricate different single-atom metal sites (e.g., Fe, Co, Ni, Zn, Cu, Mn, and Ru) anchored on the triazine-based covalent organic framework (SAS/Tr-COF) backbone with the bridging structure of metal−nitrogen−chlorine for highperformance catalytic CO 2 reduction. Remarkably, the as-synthesized Fe SAS/Tr-COF as a representative catalyst achieved an impressive CO generation rate as high as 980.3 μmol g −1 h −1 and a selectivity of 96.4%, over approximately 26 times higher than that of the pristine Tr-COF under visible light irradiation. From X-ray absorption fine structure analysis and density functional theory calculations, the superior photocatalytic performance is attributed to the synergic effect of atomically dispersed metal sites and Tr-COF host, decreasing the reaction energy barriers for the formation of *COOH intermediates and promoting CO 2 adsorption and activation as well as CO desorption. This work not only affords rational design of state-of-the-art catalysts at the molecular level but also provides in-depth insights for efficient CO 2 conversion.

A chemically bonded and plasmonic Z-scheme junction for high-performance artificial photosynthesis of hydrogen peroxide

“…Transient absorption (TA) spectroscopy was used to further investigate the kinetic behavior of the photogenerated charge carriers, especially the photoinduced charge separation at semiconductor interfaces. 38,56 The intuitive pseudo-color TA spectra of CN and CN/WO-12.5% were recorded (Fig. 3a and d).…”

Boosted charge separation in direct Z-scheme heterojunctions of CsPbBr3/Ultrathin carbon nitride for improved photocatalytic CO2reduction

“…Excessive consumption of fossil fuels and continuous emission of carbon dioxide (CO 2 ) have caused serious environmental problems. [1][2][3][4][5] Inspired by plant photosynthesis, articial photosynthesis provides promising strategies for achieving simultaneous CO 2 reduction and H 2 O oxidation into high-valued hydrocarbon fuels under mild conduction, alleviating energy crisis and environmental issues such as severe global warming and associated climate change issues. [6][7][8][9] However, this remains a huge challenge owing to the high chemical inertness of CO 2 molecules, slow kinetics of H 2 O oxidation and multi-electron transfer pathways with high reaction barriers.…”

Single-Atom Catalysts on Covalent Organic Frameworks for CO2 Reduction

“…Representative COF structures as substrates for the SACs. (a) Triazine-based COFs, (b) quinone-based COFs, (c) 2,2′-bipyridine-based COFs, (d) terpyridine-based COFs, (e) acenaphthenediimine-based COFs, (f) porphyrin-based COFs, (g) triazine-linked porphyrin-based COFs, (h) tetrathiafulvalene-linked porphyrin-based COFs, (i) phenazine-linked phthalocyanine-based COFs, and (j) dioxin-linked phthalocyanine-based COFs . (k) 3D imide-linked phthalocyanine-based COFs …”

“…In another study, a terpyridine ligand-coordinated COF containing Cu was synthesized as a photocatalytic SAC for sulfamethoxazole degradation (Figure 5d), 43 and it showed improved light absorption and realized total separation between electrons and holes. Recently, acenaphthenequinone monomers were introduced in a triazine-based COF 22 (Figure 5e) by Schiff base reaction. The novel metal−nitrogen− chlorine coordination structure provides atomic metal sites, exhibiting superior CO 2 RR photocatalytic performance of CO generation rate as high as 980.3 μmol g −1 h −1 and a selectivity of 96.4%.…”

“…Numerous transition metals, such as Ru, Cu, W, Mo, Mn, Re, and Cr, have been explored for this application. Among the N-ligand COFs, 2,2′-bipyridine COFs are the most studied, and they have exhibited high performances in both the electrocatalytic and photocatalytic ,, CO 2 RR. Lloret-Fillol et al designed a 2,2′-bipyridine COF with Mn, which showed a 10-fold improvement in electrocatalytic CO 2 RR over a Mn-based molecular catalyst.…”