Rational Design of FeNi Bimetal Modified Covalent Organic Frameworks for Photoconversion of Anthropogenic CO₂ into Widely Tunable Syngas

Abstract

Direct photoconversion of low‐concentration CO2 into a widely tunable syngas (i.e., CO/H2 mixture) provides a feasible outlet for the high value‐added utilization of anthropogenic CO2. However, in the low‐concentration CO2 photoreduction system, it remains a huge challenge to screen appropriate catalysts for efficient CO and H2 production, respectively, and provide a facile parameter to tune the CO/H2 ratio in a wide range. Herein, by engineering the metal sites on the covalent organic frameworks matrix, low‐concentration CO2 can be efficiently photoconverted into tunable syngas, whose CO/H2 ratio (1:19–9:1) is obviously wider than reported systems. Experiments and density functional theory calculations indicate that Fe sites serve as the H2 evolution sites due to the much stronger binding affinity to H2O, while Ni sites act as the CO production sites for the higher affinity to CO2. Notably, the widely tunable syngas can also be produced over other Fe/Ni‐based bimetal catalysts, regardless of their structures and supporting materials, confirming the significant role of the metal sites in regulating the selectivity of CO2 photoreduction and providing a modular design strategy for syngas production.

A novel cobalt-anchored covalent organic framework for photocatalytic conversion of CO2 into widely adjustable syngas

“…However, the production rate of syngas decreased slightly after 3 h reaction, probably caused by the partial deactivation of the photosensitizer after the prolonged reaction. 53 The apparent quantum efficiency (AQE) for syngas production under 420 nm single-wavelength irradiation was calculated to be 1.18%, which was competitive with that of most reported metal-modified COF-based photocatalytic systems under similar reaction conditions (Table S1†).…”

“…Compared with COF-TVBT-Bpy, the PL intensity of Co@COF-TVBT-Bpy decreased remarkably, and the average fluorescence lifetime ( τ = 2.5 ns) was shorter than that of COF-TVBT-Bpy ( τ = 6.5 ns), suggesting that the incorporation of Co ions could restrain the recombination of photogenerated electron–hole pairs. 53 Transient photocurrent response measurements were performed under visible-light irradiation to explore the transfer efficiency of photogenerated electrons. The photocurrent generated by the two materials exhibited reproducible response without obvious attenuation, and Co@COF-TVBT-Bpy showed higher photocurrent response intensity compared with COF-TVBT-Bpy (Fig.…”

Conductive Phthalocyanine‐Based Covalent Organic Framework for Highly Efficient Electroreduction of Carbon Dioxide

“…Recently, because of the crystalline and porous features, covalent organic frameworks (COFs) have attracted considerable attention in gas storage, catalysis, and photoelectric areas. [ 29–38 ] Particularly, integration of topologically identical and catalytically active building blocks into the porous extended structures could endow COFs to bridge a gap between homogeneous and heterogeneous catalysis. [ 39 ] Despite several COFs have been reported for CO 2 RR, the insulating nature usually leads to low current density and thus limits their application.…”

A critical review on emerging photocatalysts for syngas generation via CO2 reduction under aqueous media: a sustainable paradigm

“…Moreover, it has been found that the co-operative effect between the d-block elements such as Fe 51 and Ni 200 could feature in bimetallic active centres, which resulted in pronounced/improved photoreduction of CO 2 . Aiming towards it, very recently, Han et al 41 rationally customized a COF by integrating Fe/Ni metal sites over the surface, which was successfully utilized for photoreduction of less concentrated CO 2 into tuneable syngas (Fig. 10a–c).…”

“…Herein, we have discussed and emphasized different photoactive materials including MOFs, 28,39 organic polymers, 21,[40][41][42] POMs, 43,44 LDHs, 45,46 metal oxides, 47,48 metal complexes, 49,50 and single atom metals 51,52 for CO 2 reduction into syngas and have thus briefly described their photocatalytic activities to rationalize the stream proportion of the syngas mixture i.e. CO/H 2 or H 2 /CO.…”