Search for: All records

Chiral [Ir(N^C)₂(C^C:)] complexes are described. At room temperature they act as emitters in the red and NIR regions. Their optical and chiroptical properties were studied. Remarkably VCD and TD-DFT allow us to ascertain their stereochemistry. 

Abstract Electrochemical reduction of carbon dioxide (CO₂RR) to value‐added products is a promising strategy to alleviate the greenhouse gas effect. Molecular catalysts, such as cobalt (II) phthalocyanine (CoPc), are known to be efficient electrocatalysts that are capable of converting CO₂into carbon monoxide (CO). Herein, we report an axial modification strategy to enhance CoPc's CO₂RR performance. After coordinating with axial ligands, the electron density of Co was depleted via π‐backbonding. This π‐backbonding weakened the Co‐CO bond, resulting in rapid desorption of CO. Also, the presence axial ligands elevated the Co dz²orbital energy, resulting in a significantly enhanced CO selectivity, evidenced by an increased faradaic efficiency (FE) from 82 % (CoPc) to 91 % and 94 % with the presence of pyridine (CoPc‐py) and imidizal ligands (CoPc‐im), respectively, at −0.82 V vs. RHE. Density functional theory calculations reveal that axial ligation of CoPc can reduce the energy barrier for CO₂activation and facilitate the formation of^*COOH. 

Abstract A gas‐phase approach to form Zn coordination sites on metal–organic frameworks (MOFs) by vapor‐phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution‐phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO₂to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200–300 mV. Using element‐specific X‐ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square‐pyramidal geometry with four Zn−N bonds in the equatorial plane and one Zn‐OH₂bond in the axial plane. The fine‐tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials. 

Abstract A gas‐phase approach to form Zn coordination sites on metal–organic frameworks (MOFs) by vapor‐phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution‐phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO₂to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200–300 mV. Using element‐specific X‐ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square‐pyramidal geometry with four Zn−N bonds in the equatorial plane and one Zn‐OH₂bond in the axial plane. The fine‐tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials.