Search

Photocatalytic CO2 reduction offers a promising approach for managing global carbon balance. The smooth delivery of the photoexcited electrons to the active sites without the extra photosensitizers is still challenging. Herein, a series of donor-π-acceptor conjugated organic polymers (COPs) were produced using anthracene, cobalt-coordinated bipyridyl, and benzene as donor, acceptor, and π linker units, respectively. The introduction of phenyl linker significantly improved the activities of photocatalytic CO2 reduction upon visible light illumination. Structure-performance relationship examinations uncovered that donor-π-acceptor structure promotes mobility of charge carriers and utilization efficiency on the catalytically active sites, resulting in high photocatalytic activity and durability for CO2 photoreduction. The in-depth insights into the electron transport processes open new perspectives for further optimization and rational design of photoactive polymers with high efficiency for solar-energy conversion.

The visible-light-driven photocatalytic CO2 reduction with high efficiency is highly desirable but challenging. Herein, we present porphyrin-tetraphenylethene-based covalent organic frameworks (MP-TPE-COF, where M=H2, Co and Ni; TPE=4,4′,4″,4‴-(ethane-1,1,2,2-tetrayl) tetrabenzaldehyde; COF=covalent organic framework) as ideal platforms for understanding photocatalytic CO2 reduction at molecular level. Experimental and theoretical investigations have demonstrated crucial roles of metalloporphyrin units in selective adsorption, activation and conversion of CO2 as well as in the separation of charge carriers and electron transfer, thus allowing for flexible modulation of photocatalytic activity and selectivity. CoP-TPE-COF exhibits high CO evolution rate of 2,414 µmol g−1 h−1 with the selectivity of 61% over H2 generation under visible-light irradiation, while NiP-TPE-COF provides CO evolution rate of 525 µmol g−1 h−1 and 93% selectivity with superior durability. Moreover, the photocatalytic system is feasible for the simulated flue gas, which provides CO evolution rate of 386 µmol g−1 h−1 and selectivity of 77%. This work provides in-depth insight into the structure-activity relationships toward the activation and photoreduction of CO2.

Covalent organic frameworks (COFs) are regarded as new platforms for solar-to-chemical energy conversion due to their tailor-made functions and pre-designable structures. Their intrinsic reversibility and the high polarization of organic linkages inevitably result in poor chemical stability and weak optoelectronic properties. Herein, one N-acylhydrazone-linked COF (H-COF) was converted into a stable and π-conjugated oxadiazole-linked COF via post-oxidative cyclization. Both chemical stability and π-electron delocalization throughout the reticular framework are significantly improved, leading to a high hydrogen evolution rate of 2615 μmol g

Background Red light withering significantly improves the sensory flavor qualities of tea, although changes in metabolites during this process have not been systematically studied until now. The present study comprehensively analyzes metabolites in withered tea leaves at 2-h intervals up to 12 h under red light (630 nm) and dark conditions using ultra performance liquid chromatography-high resolution mass spectrometry (untargeted metabolomics). Results Ninety-four non-volatile compounds are identified and relatively quantified, including amino acids, catechins, dimeric catechins, flavonol glycosides, glycosidically-bound volatiles, phenolic acids and nucleosides. The results show that amino acids, catechins and dimeric catechins are most affected by red light treatment. Ten free amino acids, theaflavins and theasinensin A increase after red light irradiation, whereas epigallocatechin gallate and catechin fall. Conclusion The present study provides a comprehensive and systematic profile of the dynamic effects of red light on withering tea and a rationale for its use in tea processing quality control. © 2021 Society of Chemical Industry.

Photocatalytic CO

Photocatalytic CO2 reduction is a promising technology to mitigate environmental issue and the energy crisis. The four nitrogen atoms in the porphyrin ring can incorporate transition metals to form stable active sites for CO2 activation and photoreduction. Nevertheless, the photocatalytic efficiency of metalloporphyrins is still low due to the insufficient photoelectron injection to drive CO2 photoreduction upon visible light irradiation. To address this issue, considerable efforts have been made to introduce photosensitizers for constructing homogeneous or heterogeneous metalloporphyrin-based photocatalytic systems. In this Review, recent advances of metalloporphyrin-based materials for visible-light-driven CO2 reduction were summarized. The methods for the modulation of photosensitizing process at molecular level were presented for the promotion of photocatalytic performance. The mechanism of CO2 activation and photocatalytic conversion was illustrated. Better insight into the structure-activity relationship provides guidance to the design of metalloporphyrin-related photocatalytic systems.

Photocatalytic CO

It is of great significance to mediate the redox kinetics and shuttle effect of polysulfides in pursuit of high-energy-density and long-life lithium-sulfur (Li-S) batteries. Herein, a new strategy is proposed based on the electrostatic attraction and catalytic effect of polysulfides for the modification of the polypropylene (PP) separator. Guanidinium-based ionic-covalent organic nanosheets (iCON) on the surface of Ti3 C2 is presented as a coating layer for the PP separator. The synergetic effects of Ti3 C2 and iCON provide new platforms to suppress the shuttle effect of polysulfides, expedite the redox kinetics of sulfur species, and promote efficient conversion of the intercepted polysulfides. The functional separator endows carbon nanotube/sulfur cathodes with excellent electrochemical performance. The average capacity decay per cycle within 2000 cycles at 2 C is as low as 0.006%. The separator is even effective in the case of sulfur content of 90 wt% and sulfur loading of 7.6 mg cm-2 ; the reversible capacity, areal capacity, and volumetric capacity at 0.1 C are as high as 1186 mA h g-1 , 9.01 mA h cm-2 , and 1201 mA h cm-3 , respectively. This work provides a promising approach toward separator modification for the development of high-performance Li-S batteries.

Artificial transistors represent an ideal means for meeting the requirements in interfacing with biological systems. It is pivotal to develop new proton-conductive materials for the transduction between biochemical events and electronic signals. Herein, the first demonstration of a porous organic polymer membrane (POPM) as a proton-conductive material for protonic field-effect transistors is presented. The POPM is readily prepared through a thiourea-formation condensation reaction. Under hydrated conditions and at room temperature, the POPM delivers a proton mobility of 5.7 × 10-3 cm2 V-1 s-1 ; the charge carrier densities are successfully modulated from 4.3 × 1017 to 14.1 × 1017 cm-3 by the gate voltage. This study provides a type of promising modular proton-conductive materials for bioelectronics application.