Silver frameworks based on a tetraphenylethylene-imidazole ligand for electrocatalytic reduction of CO2 to CO.

Metal-organic frameworks (MOFs) can be used as electrocatalysts for the CO2 reduction reaction (CO2RR) because of their well-dispersed metal centers. Silver is a common electrocatalyst for reduction of CO2 to CO. In this study, two Ag-MOFs with different structures of [Ag8O2(TIPE)6](NO3)4 (Ag-MOF1) and [Ag(TIPE)0.5CF3SO3] (Ag-MOF2) [TIPE = 1,1,2,2-tetrakis(4-(imidazol-1-yl)phenyl)ethene] were synthesized and used for CO2 electroreduction. The results show that Ag-MOF2 is superior to Ag-MOF1 and exhibits high CO faradaic efficiency (FE) of 92.21% with partial current density of 29.51 mA cm-2 at -0.98 V versus reversible hydrogen electrode (RHE). The FECO is higher than 80% in the potential range of -0.78 to -1.18 V. The difference may be caused by different framework structures leading to different electrochemical active surface areas and charge transfer kinetics. This study provides a new strategy for designing and constructing CO2 electroreduction catalysts and provides potential ways for solving environmental and energy problems caused by excessive CO2 emission.

Supramolecular assemblies of Cu(II) with a tetraphenylethene-imidazole ligand for tuning photocatalytic CO2 reduction.

Cu(II) supramolecular assemblies [Cu2(tipe)2(H2O)2](NO3)4·2.5H2O (CuN4) and [Cu2Cl4(tipe)(CH3CN)]·H2O (CuN2Cl2) (tipe = 1,1,2,2-tetrakis(4-(imidazole-1-yl)phenyl)ethene) were synthesized and utilized for photocatalytic CO2 reduction. CuN4 exhibits CO production of up to 891 µmol gcat-1 with a selectivity of 79.9%, while CuN2Cl2 gives low CO production of 206 µmol gcat-1 but with a high selectivity of >99.9% in 5 h. The experimental and DFT calculation results indicate that the coordination environment and non-covalent interactions within the assemblies have a great impact on the photocatalytic CO2 reduction behavior. This work provides useful insights on Cu(II) assembly catalyzed CO2 photoreduction.

Fluorescent Zn(II) frameworks with multicarboxylate and pyridyl N-donor ligands for sensing specific anions and organic molecules.

Three novel fluorescent Zn(II) frameworks, namely [Zn(DPA)(NDA)]2·2DMF (1), [Zn2(DPA)(OBA)2]·2DMF·4H2O (2) and [Zn(DPA)(HNTB)]·H2O (3) (DPA = 2,5-di(pyridin-4-yl)aniline, H2NDA = 1,4-naphthalenedicarboxylic acid, H2OBA = 4,4'-oxydibenzoic acid, H3NTB = 4,4',4''-nitrilotribenzoic acid, DMF = N,N-dimethylformamide), were successfully fabricated and structurally characterized. Due to the variety of organic linkers, 1-3 exhibit varied topologies: 1 is a 4-c three-dimensional (3D) framework with {65·8} topology, 2 is a 6-c 3D net with point symbol of {44·610·8}, and 3 is a 4-c two-dimensional network that further stacks into a 3D structure by hydrogen bonding interactions with {44·62} topology. Experiments related to fluorescence show that 1-3 can be utilized to quickly identify specific anions of CrO42-/Cr2O72-, and organic molecules such as 2,4,6-trinitrophenol and benzaldehyde.