Ferrocene-Functionalized Crystalline Biomimetic Catalysts for Efficient CO2 Photoreduction.

Photoreducing carbon dioxide (CO2) into highly valued chemicals or energy products has been recognized as one of the most promising proposals to degrade atmospheric CO2 concentration and achieve carbon neutrality. Adenine with a photosensitive amino group and aromatic nitrogen atom can strongly interact with CO2 and has been authenticated for its catalytic activity for the CO2 photoreduction reaction (CO2RR). Herein, two adenine-constructed crystalline biomimetic photocatalysts (Co2-AW and Co2-AF) were designed and synthesized to achieve CO2RR. Between them, Co2-AF displayed higher photocatalytic activity (225.8 µmol g-1 h-1) for CO2-to-HCOOH conversion than that of Co2-AW. It was found that the superior charge transfer capacity of the functional ferrocene group in Co2-AF is the primary reason to facilitate the photocatalytic performance efficiently. Additionally, this work also demonstrated the great potential of the ferrocene group as an electron donor and mediator in improving the photocatalytic activity of crystalline coordination catalysts.

Adenine Components in Biomimetic Metal-Organic Frameworks for Efficient CO2 Photoconversion.

Visible-light driven photoconversion of CO2 into energy carriers is highly important to the natural carbon balance and sustainable development. Demonstrated here is the adenine-dependent CO2 photoreduction performance in green biomimetic metal-organic frameworks. Photocatalytic results indicate that AD-MOF-2 exhibited a very high HCOOH production rate of 443.2 µmol g-1 h-1 in pure aqueous solution, and is more than two times higher than that of AD-MOF-1 (179.0 µmol g-1 h-1 ) in acetonitrile solution. Significantly, experimental and theoretical evidence reveal that the CO2 photoreduction reaction mainly takes place at the aromatic nitrogen atom of adenine molecules through a unique o-amino-assisted activation rather than at the metal center. This work not only serves as an important case study for the development of green biomimetic photocatalysts used for artificial photosynthesis, but also proposes a new catalytic strategy for efficient CO2 photoconversion.

A new supramolecular catalytic system: the self-assembly of Rh8 cage host anthracene molecules for [4 + 4] cycloaddition induced by UV irradiation.

The supramolecular assembly, used as a molecular reactor, is of great significance in host-guest chemistry. In this work, we used a tetratopic pyridyl ligand as a building block to hierarchically combine a slightly twisted cuboid with half-sandwich rhodium fragments. The cuboid directionally self-assembled hydrophobic pockets that can encapsulate conjugated molecules like anthracene (ANT) as guests in solutions, by supramolecular interactions including hydrogen bonding and hydrophobic interactions. The array of the ANT molecules in the confined pockets was subjected to a [4 + 4] photocycloaddition reaction under UV light irradiation as an external stimulus in a methanol solution. Furthermore, the mechanism underlying the process was proposed. The cuboid was fully characterized by 1H NMR, single-crystal X-ray diffraction (SCXRD), and mass spectrometry (MS), and its host-guest and cycloaddition processes were monitored by 1H NMR spectroscopy and UV-visible spectrophotometry.

Hydrophobic Polyoxometalate-Based Metal-Organic Framework for Efficient CO2 Photoconversion.

A novel polyoxometalate (POM)-based metal-organic framework, TBA5[P2Mo16VMo8VIO71(OH)9Zn8(L)4] (NNU-29), was in situ synthesized and applied into CO2 photoreduction. The selection of porous material containing a reductive POM cluster is considered to be helpful for CO2 reduction; meanwhile, a hydrophobic-group-modified organic ligand enables NNU-29 to exhibit good chemical stability and restrains hydrogen generation to some extent. In the photocatalytic CO2 reduction, the yield of HCOO- reached 35.2 µmol in the aqueous solution with selectivity of 97.9% after 16 h.