Oriented electron transmission in polyoxometalate-metalloporphyrin organic framework for highly selective electroreduction of CO2

Abstract

The design of highly stable, selective and efficient electrocatalysts for CO2 reduction reaction is desirable while largely unmet. In this work, a series of precisely designed polyoxometalate-metalloporphyrin organic frameworks are developed. Noted that the integration of {ε-PMo8VMo4VIO40Zn4} cluster and metalloporphyrin endows these polyoxometalate-metalloporphyrin organic frameworks greatly advantages in terms of electron collecting and donating, electron migration and electrocatalytic active component in the CO2 reduction reaction. Thus-obtained catalysts finally present excellent performances and the mechanisms of catalysis processes are discussed and revealed by density functional theory calculations. Most importantly, Co-PMOF exhibits remarkable faradaic efficiency ( > 94%) over a wide potential range (−0.8 to −1.0 V). Its best faradaic efficiency can reach up to 99% (highest in reported metal-organic frameworks) and it exhibits a high turnover frequency of 1656 h−1 and excellent catalysis stability ( > 36 h).

Synergistic electroreduction of carbon dioxide to carbon monoxide on bimetallic layered conjugated metal-organic frameworks

“…2f reveal that no heavy backscattering atoms (Zn) are bound to Zn sites in PcCu-O 8 -Zn 43,44 . Therefore, the XANES and EXAFS spectra of PcCu-O 8 -Zn together with the contrast experiments provide solid proof for the existence of square planar complexes via the coordination of PcCu(II)-(OH) 8 to Zn (II) ions.…”

“…This so-called syngas mixture with varying molar ratios of H 2 /CO is commonly used as precursor for hydroformylation process (H 2 : CO = 1:1), methanol synthesis of Fischer−Tropsch process (H 2 : CO = 2:1) and methanation process (H 2 :CO = 3:1) to produce high-value/energy-dense hydrocarbons/alcohols 5,6 . However, the CO 2 -to-CO conversion, involving the transfer of two electrons and two protons, typically suffers from high kinetic barriers and low selectivity due to the high thermodynamic/kinetic stability of CO 2 and the competing hydrogen evolution reaction (HER) in aqueous media, respectively 7,8 . Recently, great efforts have been dedicated to explore numerous electrocatalysts for catalytic CO 2 RR to CO, including noble metals (Au, Pd, Ag), transitionalmetal-based materials (Fe, Co, Ni, Cu, Zn) and heteroatom-doped porous carbons 2,7,[9][10][11][12][13][14][15][16][17] .…”

“…Metal-organic frameworks (MOFs) are one class of highly ordered crystalline coordination polymers, which are emerging as highly attractive catalytic systems due to the uniquely combining homogenous and heterogeneous features: First, the incorporation of well-defined and highly active sites into a defined and stable scaffold ensures excellent catalytic activity and selectivity; second, the porous metrics allow for sufficient and controllable mass transfer to and from the embedded active sites; finally, the molecularly defined catalytic environment around the active site allows for tuning the catalytic reaction by modifying the scaffold and facilitates deriving fundamental understanding of catalytic mechanism. For example, Co-PMOF and Al 2 (OH) 2 TCPP-Co MOFs have been developed for electrocatalytic CO 2 RR to CO with high selectivity (>70%) 8,13,18 . However, conventional MOFs suffer from certain drawbacks including their intrinsically low conductivity (electrical insulators) and the blockage of metal centers by organic ligands, which have greatly hampered their development for promoting CO 2 RR.…”

Metal-organic frameworks for electrochemical reduction of carbon dioxide: The role of metal centers

“…More recently, Lan and co-workers prepared polyoxometalate (POM)-metalloporphyrin organic frameworks (M-PMOF) with hydrothermal method [100] . They tested the electrocatalytic properties toward the CO 2 RR in CO 2 -saturated 0.5 M KHCO 3 electrolyte http://engine.scichina.com/doi/10.1016/j.jechem.2019.04.013 and observed that Co-PMOF exhibited remarkable faradaic efficiency (99%) of CO production.…”

“…(a) The free energy diagrams of CO 2 reduction to CO for different catalysts, * denotes a surface active site; (b) The free energy for * COOH formation ( G 1 ), * CO formation ( G 2 ), and CO desorption process ( G 3 ) during CO 2 RR; (c,d) The proposed mechanism for the CO 2 RR over Co-PMOF catalysts (POM represents electron-donating species, porphyrin is charge transfer ligand and transition metals represent electron-collecting species). Reproduced with permission[100] . Copyright 2018, springer.…”