Visible-light-driven photocatalytic CO₂ reduction to formate over a zirconium-porphyrin metal–organic framework with shp-a topology

Abstract

In this study, a zirconium-porphyrin MOF (PCN-223) was synthesized, characterized and applied in the visible-light-driven photocatalytic CO2 reduction. Draw support from highly conjugated 4-connected TCPP ligand and 12-connected zirconium based...

Photoreactive Carbon Dioxide Capture by a Zirconium–Nanographene Metal–Organic Framework

“…Finally, the CO 2 /formate conversion shown in Scheme involve a “two-for-one” approach, where a single photon triggers a cascade of electron/hydrogen atom transfers. Similar two-electron sensitization processes have been reported previously, and they include the reverse reaction: the conversion of formate to CO 2 . − The “two-for-one” CO 2 -to-formate reduction demonstrated here is likely responsible for high formate selectivity observed here and in many other photochemical CO 2 conversion experiments involving light-responsive Zr-based MOFs. − , We anticipate that the “two-for-one” mechanism will be a valuable tool for future CO 2 reduction catalysts with improved formate selectivity.…”

“…73−75 The "two-for-one" CO 2to-formate reduction demonstrated here is likely responsible for high formate selectivity observed here and in many other photochemical CO 2 conversion experiments involving lightresponsive Zr-based MOFs. [20][21][22][23][24][25][26]38 We anticipate that the "two-for-one" mechanism will be a valuable tool for future CO 2 reduction catalysts with improved formate selectivity.…”

Photoreactive CO2 Capture by a Zr-Nanographene MOF

“…Even in the absence of any additional catalytic units, Zr-based MOFs have been shown to photocatalytically convert CO2 selectively to the formate ion. While the catalytic performance has been reported in many studies, [16][17][18][19][20][21][22]34 the catalytic site responsible for conversion and mechanistic details remain unclear. This is in contrast to Ti-based MOFs with small organic ligands, such as NH2-MIL-125(Ti), for which an evident photochromic effect, unambiguous electron paramagnetic resonance (EPR) spectroscopy data and transient absorption (TA) photolysis experiments confirm that the photoinduced generation of Ti(III) ions occurs from ligand to metal charge transfer (LMCT) excited states and that these reduced node metal centers are responsible for catalytic conversion of CO2 to HCOO -.…”

“…Many studies on Zr-MOFs for photocatalytic CO2 reduction have provided EPR, UV-Vis diffuse reflectance, photoluminescence, and ultrafast transient absorption data showing evidence of charge transfer from excited state ligand to Zr-oxo cluster, reduction of Zr 4+ to Zr 3+ and subsequent CO2 to formate reduction by Zr 3+ . [16][17][18][19][20][21][22]34 In contrast, other studies controvert the possibility of node reduction, based on the lack of EPR signal ascribable to Zr(III) and lack of photocatalytic activity in Zr-MOFs. 36, 37 Computational studies indicate that the empty d-orbital of Zr do not overlap with the ligand π* orbital and that electronic transitions in Zr-MOFs are purely ligand-based and cannot result in formation of Zr(III) via LMCT.…”

“…[63][64][65] The "two-for-one" CO2-to-formate reduction demonstrated here is likely responsible for high formate selectivity observed here and in many other photochemical CO2 conversion experiments involving light-responsive Zr-based MOFs. [16][17][18][19][20][21][22]34 We anticipate that the "two-for-one" mechanism will be a valuable tool for future CO2 reduction catalysts with improved formate selectivity.…”