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Photocatalytic CO2 reduction to valuable chemicals, especially fuels, is considered as a promising strategy to mitigate CO2 accumulation and tackle the energy crisis, among which photocatalysis is vital to achieve efficient and selective reduction of CO2. In this work, phosphorus-doped hollow polygonal g-C3N4 rods were prepared through phosphoric acid assisted self-assembly under hydrothermal conditions and subsequent thermal polymerization using phosphoric acid as the phosphorus source and melamine as the nitrogen-rich precursor. The resulting phosphorus-doped hollow polygonal g-C3N4 rods feature increased specific surface area, visible light absorption and photogenerated carrier separation and transfer efficiency according to the structure and photoelectric properties characterization. Coupled with an earth abundant metal-based complex, i.e. [Co(bpy)3]Cl2, as a co-catalyst, the phosphorus-doped hollow polygonal g-C3N4 rods deliver a CO evolution rate of up to 447.5 μmol g−1 h−1 with a selectivity of ca. 96%, being much higher compared to the pristine g-C3N4 (67.01 μmol g−1 h−1 with a selectivity of ca. 94%) resulting from the improved light harvesting and charge transfer to the co-catalyst. Remarkably, the phosphorus-doped hollow polygonal g-C3N4 rods can be reused 6 times while retaining constant catalytic activity in the photoreduction reaction. This work presents new insights into photocatalytic CO2 reduction by developing non-metal doping and hollow structural designs for semiconductor photocatalysts. [ABSTRACT FROM AUTHOR]

The photocatalytic reduction of CO2 into fuels offers the prospect for creating a new CO2 economy. Harnessing visible light‐driven CO2‐to‐CO reduction mediated by the long‐lived triplet excited state of rhenium(I) tricarbonyl complexes is a challenging approach. We here develop a series of new mononuclear rhenium(I) tricarbonyl complexes (Re‐1−Re‐4) based on the imidazole‐pyridine skeleton for photo‐driven CO2 reduction. These catalysts are featured by combining pyridyl‐imidazole with the aromatic ring and different pendant organic groups onto the N1 position of 1,3‐imidazole unit, which display phosphorescence under Ar‐saturated solution even at ambient conditions. By contrast, {Re[9‐(pyren‐1‐yl)‐10‐(pyridin‐2‐yl)‐9H‐pyreno[4,5‐d]imidazole)](CO)3Cl} (Re‐4) by introducing pyrene ring at the N1 position of pyrene‐fused imidazole unit exhibits superior catalytic performance with a higher turnover number for CO (TONCO=124) and >99.9 % selectivity, primarily ascribed to the strong visible light‐harvesting ability, long‐lived triplet lifetimes (164.2 μs) and large reductive quenching constant. Moreover, the rhenium(I) tricarbonyl complexes derived from π‐extended pyrene chromophore exhibit a long lifetime corresponding to its ligand‐localized triplet state (3IL) evidenced from spectroscopic investigations and DFT calculations. [ABSTRACT FROM AUTHOR]

An unprecedented strategy has been developed involving the earth-abundant Cu-catalyzed hydrocarboxylation of alkynes with HCOOH to (E)-acrylic derivatives with high regio- and stereoselectivity via synergistic effects with ppm levels of a Pd catalyst. Both symmetrical and unsymmetrical alkynes bearing various functional groups were successfully hydrocarboxylated with HCOOH, and the modification of a pharmaceutical molecule exemplified the practicability of this process. This protocol employs HCOOH as both a CO surrogate and hydrogen donor with 100% atom economy and it can be viewed as an alternative approach for indirect CO2 utilization. Mechanistic investigations indicate a Cu/ppm Pd cooperative catalysis mechanism via alkenylcopper species as potential intermediates formed from Cu-hydride active catalytic species with HCOOH as a hydrogen source. This bimetallic system involving inexpensive Cu and trace Pd provides a reliable and efficient hydrocarboxylation method to access industrially useful acrylic derivatives with HCOOH as a hydrogen source, and it provides novel clues for optimizing other Cu–H-related co-catalytic systems. [ABSTRACT FROM AUTHOR]

Significant efforts have been devoted to the photochemical CO2 reduction reaction (CO2RR) as a significant pathway for the development of renewable energy systems. However, the competitive hydrogen evolution reaction (HER) greatly impedes the fundamental understanding and industrial application of the CO2RR. Herein, we report polyhedral oligomeric silsesquioxane (POSS)-based porous organometallic polymers (POMPs) that are able to catalyze the photochemical CO2RR to produce syngas. Their surface area, CO2 adsorption ability, visible-light harvesting capacity and photoinduced electron–hole separation efficiency can be regulated by tuning the Re-bipyridine content in POMPs. Consequently, the effects of these properties on CO2RR and HER activities have been investigated and the surface area and electron transfer efficiency of these materials have been elucidated as the key points. Importantly, we also reveal the applicability of the developed strategy in designing new catalysts for the CO2RR. [ABSTRACT FROM AUTHOR]

Developing effective sunlight-driven systems for CO2 reduction is one of the most promising subjects from the perspective of sustainably producing solar fuels. Herein, we develop a strategy to boost CO2 reduction performance by enhancing intermolecular electron transfer efficiency and visible light-absorption ability by introducing bifunctional pyrene groups on the ligand. This catalyst exhibits high-efficiency performance for natural light-powered CO2 reduction (TONCO up to 350 ± 36, ΦCO up to 46.6 ± 3%). This is the first report on using a single-molecule photocatalyst for CO2 reduction under natural conditions. Through the combination of experimental results and DFT calculations, the appending pyrene groups have been proven to promote the catalyst's ability to harness visible light as well as facilitate electron transfer (ET) through intermolecular π–π interactions. Due to the accelerated intermolecular ET, TONCO can be further boosted up to 1367 ± 32 in the presence of the ruthenium photosensitizer. Moreover, an enhancement in CO2 electroreduction performance can also be observed for the pyrenyl-functionalized rhenium catalyst further highlighting the versatile applications of this methodology. [ABSTRACT FROM AUTHOR]

Developing an efficient and easy‐to‐handle strategy in designing catalysts for CO2 reduction into CO by harnessing sunlight is a promising project. Here, a facile strategy was developed to design a Re catalyst modified with an ionic secondary coordination sphere for photoreduction of CO2 to CO by visible light. By adding ionic liquids or tuning a different ionic secondary coordination sphere, it was discovered that an outstanding optical property, other than CO2 absorption ability or the ability to dissociation of chloride anion, is the prerequisite for catalyst design. Accordingly, a novel Re catalyst, {Re[BpyMe(tris(2‐hydroxyethyl)amine)](CO)3Cl}Br (Re‐THEA), was designed, screened, and resulted in a relative high quantum yield (up to 34 %) for visible‐light‐induced CO2 reduction with a single‐molecule system. DFT calculations, combined with experimental outcomes, suggested the pendant ionic tris(2‐hydroxyethyl)amino (THEA) group on Re‐THEA can enhance visible‐light absorption, stabilize reaction intermediates, and suppress the Re–Re dimer formation. [ABSTRACT FROM AUTHOR]

With the increasing awareness of sustainable chemistry and green chemistry, photochemical CO2 fixation has drawn more and more attention in response to the need for renewable C1 resources and inexhaustible clean energy resources. It is appealing to provide carboxylic acids and derivatives using CO2 as a renewable feedstock, which is widely used in the manufacture of pharmaceuticals, pesticides, dyes and other fine chemicals. Classifying them by the types of reaction sites, this review presents an overview of the recent advances and achievements in the photocarboxylation of C(sp3)–X (X = H, N) bonds, C(sp2)–X (X = H, N, (pseudo)halide) bonds and C(sp)–H bonds with CO2, with an emphasis on the mechanistic aspects of the reactions and a perspective on their future prospects, hopefully stimulating the further research and development of this appealing field. [ABSTRACT FROM AUTHOR]

A highly efficient carboxylative cyclization of propargylic alcohols with CO2 under atmospheric pressure catalyzed by silver (0) nanoparticles decorated reduced graphene oxide (Ag‐rGO) is reported. Ag‐rGO was fully characterized by scanning electron microscope spectra (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT‐IR) spectra, Raman spectra and X‐ray photoelectron spectroscopy (XPS). Notably, Ag‐rGO can be also applied to the construction of other value‐added chemicals (β‐oxopropylcarbamates and 2‐oxazolidinones) from CO2 at ambient conditions. In addition, Ag‐rGO is stable and reusable, which shows the potential for the practical application for CO2 capture and utilization (CCU). [ABSTRACT FROM AUTHOR]

A visible‐light‐promoted metal‐free carboxylative cyclization of propargylic amines with CO2 was shown to offer exo‐iodomethylene 2‐oxazolidinones. Incorporation of both CO2 and iodo moieties into these compounds was realized efficiently. The mechanism study revealed that this carboxylative cyclization proceeds through a radical pathway. Notably, the iodine‐functionalized 2‐oxazolidinone as a platform molecule could be easily converted into a wide range of value‐added chemicals through Buchwald–Hartwig, Suzuki, Sonogashira, photocatalytic ene, and photoreduction reactions. As a result, the plentiful downstream transformations remarkably enhance the range of chemicals derived from CO2 and open a potential avenue for CO2 functionalization to circumvent energy challenges in this field. [ABSTRACT FROM AUTHOR]

Summary of main observation and conclusion: Converting CO2 into value‐added chemicals represents a promising way to alleviate the CO2 derived environmental issues, for which the development of catalysts with high efficiency and recyclability is very desirable. Herein, the catalytic system by combining cobalt source and ionic liquid (IL) has been developed as the efficacious and recyclable catalyst for the carboxylative cyclization of propargylic amine and CO2 to prepare 2‐oxazolinones. In this protocol, various propargylic amines were successfully transformed into the corresponding 2‐oxazolinones with CoBr2 and diethylimidazolium acetate ([EEIM][OAc]) as the catalyst under atmospheric CO2 pressure. It is worth noting that the turnover number (TON) of this transformation can be up to 1740, presumably being attributed to the cooperative effect of the cobalt and IL. Furthermore, the existence of IL enables the catalytic system to be easily recycled to 10 times without losing its activity. [ABSTRACT FROM AUTHOR]