Combination of Co2+-immobilized covalent triazine framework and TiO2 by covalent bonds to enhance photoreduction of CO2 to CO with H2O

Design and synthesis of a covalent organic framework bridging CdS nanoparticles and a homogeneous cobalt–bipyridine cocatalyst for a highly efficient photocatalytic CO2reduction

“…Considering unavoidable time-consuming multistep synthesis, purification process and degradation of these complexes, in situ assembly of earth-abundant metal complexes is a promising technique, wherein significant progress has been made to date. 36–39 The in situ formation of [Co(bpy) 3 ] 2+ (bpy: 2,2′-bipyridine) for heterogeneous CO 2 photoreduction has attracted substantial attention, because [Co(bpy) 3 ] 2+ can effectively and selectively convert CO 2 to CO. 40,41 Nevertheless, the interaction between photocatalysts and homogeneous [Co(bpy) 3 ] 2+ is still rarely evaluated and reported. 42 Using porous materials containing bpy moieties as “bridges” enables killing two birds with one stone: first, bpy moieties can strongly interact with [Co(bpy) 3 ] 2+ via coordinate bonds, 30 thereby easing the electron transfer to the cocatalyst, while active [Co(bpy) x ] + separates from heterogeneous photocatalysts and makes spaces for other unactive [Co(bpy) 3 ] 2+ species, 43,44 maintaining intrinsic high activity and selectivity of [Co(bpy) 3 ] 2+ solution; second, the incorporation of these materials with other semiconductors can promote charge carrier separation, suppress charge recombination, and improve solar light utilization.…”

From conventional inorganic semiconductors to covalent organic frameworks: advances and opportunities in heterogeneous photocatalytic CO2 reduction

“…When Co 2+ ions were added, the hybrid system TiO 2 @CTF-Py produced CO at a rate of 43.34 μmol g −1 h −1 , in aqueous solution and without the addition of photosensitizers or sacrificial electron donors, exceeding the rates of the pristine CTF-Py by 5 and that of TiO 2 by 7 times. 165 The proposed CO 2 photoreduction mechanism involves a Z-scheme, where electrons tend to remain on the CTF-Py surface for CO 2 reduction and holes on the TiO 2 surface for water oxidation. Similar hybrid systems using TiO 2 as inorganic platform have been reported in the literature, showing similar CO generation rates under photocatalytic conditions analogous to the COF-hybrid systems described above.…”

“…Fig.13Synthesis route of the CTF-Py COF and the heterogeneous catalyst TiO 2 @CTF-Py. Reproduced with permission 165. Copyright 2021, Elsevier.…”

Comprehensive Review for an Efficient Charge Transfer in Single Atomic Site Catalyst/Organic Polymers toward Photocatalytic CO2 Reduction

“…The photocatalytic CO 2 reduction with H 2 O as sacrificial agents is challenging in terms of efficiency and selectivity since the valance band of CTF is not suitable for H 2 O oxidation. The fabrication of heterojunction between CTF and inorganic semiconductor that can drive water oxidation has been demonstrated by Xu et al [245] TiO 2 with a suitable band position for H 2 O oxidation was coupled with Co 2+ -immobilized pyridinebased CTF. The material shows better charge separation and enhanced photocatalytic CO 2 reduction to CO under water as the solvent and sacrificial agents.…”