Ferric Porphyrin-Based Porous Organic Polymers for CO₂ Photocatalytic Reduction to Syngas with Selectivity Control

Abstract

Visible light-induced photocatalytic CO2 reduction reaction (CO2RR) is a feasible and promising option to tackle the greenhouse effect and energy crisis. Herein, two ferric porphyrin-based porous organic polymer semiconductors, hereafter referred to as POPn-Fe (porous organic polymers, n = 1 or 2, corresponding to a benzene/biphenyl unit as a linker between porphyrin units), are synthesized for the visible light-driven CO2RR to produce syngas. The CO/H2 evolution rates for POP2-Fe under irradiation >420 nm are found to successfully reach up to 3043 and 3753 μmol g–1 h–1, respectively. Interestingly, the experiment results imply that the ferric porphyrin site could be responsible for CO evolution and the uncoordinated porphyrin unit in POPn or POPn-Fe semiconductors may be obligate for H2 formation. Furthermore, as evidenced by Mott–Schottky plots, the extended π-conjugation with the biphenyl linker makes POP2-Fe a lower conduction band potential, which helps the ferric porphyrin sites capture electrons from the photosensitizer, thus producing more CO to realize selectivity control. Also, the efficient catalytic activity of POP2-Fe is presumably attributed to the accelerated charge transfer as well as facilitates photogenerated electron and hole separation. This work offers an elegant strategy to design and optimize earth-abundant metal visible light photocatalysis for CO2 reduction to syngas with CO/H2 ratio control.

Exploiting consecutive photoinduced electron transfer (ConPET) in CO2 photoreduction

“…2 Photosensitizers that can absorb a photon and undergo photoinduced electron transfer are therefore widely employed in a number of CO 2 photoreduction systems. For instance, metal complexes such as [Ru(bpy) 3 ] 2+ , 3 Ir(ppy) 3 1 a and luminescent Cu( i ) complexes, 4 organic dyes such as 9CNA 5 and phenoxazines, 6 and quantum dots such as CuInS 2 7 and CdS 8 have been utilized as efficient light-absorbing photosensitizers. The organic 1,2,3,5-Tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) is known as a typical thermally activated delayed fluorescence (TADF) compound for tremendous application in organic light-emitting diodes and photocatalysis.…”

A zinc porphyrin polymer as efficient bifunctional catalyst for conversion of CO2 to cyclic carbonates

“…The existence of quaternization N and iodide ions was also examined by XPS analysis of [ZnPy + CPP‐BTA]I − (Figure 4). The high‐resolution XPS spectrum of N 1s exhibits a characteristic peak at 401.4 eV that confirms the formation of the quaternization N by partial pyridine and imidazole linker with methyl iodide, while the free pyridinic N and pyrrolic N of the porphyrin ring produce peaks at 398.3 and 399.9 eV, respectively (Figure 4b) [33, 44]. Moreover, Figure 4c shows that the XPS spectra of the I 3d exhibited two peaks at 618.1 and 629.7 eV, attributing to I 3d 5/2 and I 3d 3/2 , respectively [29, 32].…”

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

“…Keeping in view of the above observation, Yao et al 120 demonstrated that Fe metal incorporated POPs i.e. , ferric porphyrin-based POPs ( i.e.…”