Cobalt-based Polymerized Porphyrinic Network for Visible-light-driven CO2 Reduction.

Visible-light-driven conversion of carbon dioxide to valuable compounds and fuels is an important but challenging task due to the inherent stability of the CO2 molecules. Herein, we report a series of cobalt-based polymerized porphyrinic network (PPN) photocatalysts for CO2 reduction with high activity. The introduction of organic groups results in the addition of more conjugated electrons to the networks, thereby altering the molecular orbital levels within the networks. This integration of functional groups effectively adjusts the levels of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). The PPN(Co)-NO2 exhibits outstanding performance, with a CO evolution rate of 12 268 µmol/g/h and 85.8% selectivity, surpassing most similar photocatalyst systems. The performance of PPN(Co)-NO2 is also excellent in terms of apparent quantum yield (AQY) for CO production (5.7% at 420 nm). Density functional theory (DFT) calculations, time-resolved photoluminescence (TRPL), and electrochemical tests reveal that the introduction of methyl and nitro groups leads to a narrower energy gap, facilitating a faster charge transfer. The coupling reaction in this study enables the formation of stable C-C bonds, enhancing the structural regulation, active site diversity, and stability of the catalysts for photocatalytic CO2 reduction. This work offers a facile strategy to develop reliable catalysts for efficient CO2 conversion.

Ligand Defect-Induced Active Sites in Ni-MOF-74 for Efficient Photocatalytic CO2 Reduction to CO.

The conversion of CO2 into valuable carbon-based products using clean and renewable solar energy has been a significant challenge in photocatalysis. It is of paramount importance to develop efficient photocatalysts for the catalytic conversion of CO2 using visible light. In this study, the Ni-MOF-74 material is successfully modified to achieve a highly porous structure (Ni-74-Am) through temperature and solvent modulation. Compared to the original Ni-MOF-74, Ni-74-Am contains more unsaturated Ni active sites resulting from defects, thereby enhancing the performance of CO2 photocatalytic conversion. Remarkably, Ni-74-Am exhibits outstanding photocatalytic performance, with a CO generation rate of 1380 µmol g-1 h-1 and 94% CO selectivity under visible light, significantly surpassing the majority of MOF-based photocatalysts reported to date. Furthermore, experimental characterizations reveal that Ni-74-Am has significantly higher efficiency of photogenerated electron-hole separation and faster carrier migration rate for photocatalytic CO2 reduction. This work enriches the design and application of defective MOFs and provides new insights into the design of MOF-based photocatalysts for renewable energy and environmental sustainability. The findings of this study hold significant promise for developing efficient photocatalysts for CO2 reduction under visible-light conditions.

Amino-Functionalized Microporous MOFs for Capturing Greenhouse Gases CF4 and NF3 with Record Selectivity.

The capture and separation of fluorinated gases (F-gases) from N2 has the potential to not only reduce greenhouse gas emissions but also provide economic benefits for the semiconductor industry. In this work, two Ni-based metal-organic frameworks (MOFs), Ni-MOF (Ni(ina)2, ina = isonicotinic acid) and amine-functionalized NH2-Ni-MOF (Ni(3-ain)2, 3-ain = 3-aminoisonicotinic acid), were constructed for capturing F-gases (CF4 and NF3). At ambient conditions, both materials exhibit very high CF4 sorption capacities (2.92 mmol g-1 for Ni-MOF and 2.69 mmol g-1 for NH2-Ni-MOF). In addition, NH2-Ni-MOF exhibited a record selectivity of 46.3 for the CF4/N2 mixture at 298 K and 100 kPa, surpassing all benchmark adsorbents, including Ni-MOF (34.7). The kinetic adsorption tests demonstrated that Ni-MOF and NH2-Ni-MOF performed well for CF4/N2 and NF3/N2 mixtures. According to grand canonical Monte Carlo (GCMC) simulations, CF4 or NF3 interacts with NH2-Ni-MOF by multiple van der Waals interactions, resulting in stronger interaction than N2. More importantly, dynamic breakthrough experiments verified the practical separation potential of the two materials for CF4/N2 and NF3/N2 mixtures.