Interpenetrating 3D Covalent Organic Framework for Selective Stilbene Photoisomerization and Photocyclization

The selective photoisomerization or photocyclization of stilbene to achieve value upgrade is of great significance in industry applications, yet it remains a challenge to accomplish both of them through a one-pot photocatalysis strategy under mild conditions. Here, a sevenfold interpenetrating 3D covalent organic framework (TPDT-COF) has been synthesized through covalent coupling between N,N,N,N-tetrakis(4-aminophenyl)-1,4-benzenediamine (light absorption and free radical generation) and 5,5′-(2,1,3-benzothiadiazole-4,7-diyl)bis[2-thiophenecarboxaldehyde] (catalytic center). The thus-obtained sevenfold interpenetrating structure presents a functional pore channel with a tunable photocatalytic ability and specific pore confinement effect that can be applied for selective stilbene photoisomerization and photocyclization. Noteworthily, it enables photogeneration of cis-stilbene or phenanthrene with >99% selectivity by simply changing the gas atmosphere under mild conditions (Ar, SeleCis. > 99%, SelePhen. 2, SeleCis. Phen. > 99%). Theoretical calculations prove that different gas atmospheres possess varying influences on the energy barriers of reaction intermediates, and the pore confinement effect plays a synergistically catalytic role, thus inducing different product generation. This study might facilitate the exploration of porous crystalline materials in selective photoisomerization and photocyclization

Electronic Tuning of Active Sites in Bifunctional Covalent Organic Frameworks for Photoassisted CO₂ Electrocatalytic Full Reaction

Realizing simultaneously energy-efficiency improvement and green economic implementation remains a daunting challenge in addressing the low-efficiency issues of CO2 electroreduction to meet the sustainable development strategy. Here, we propose a series of porphyrin-based COFs (TTCOF-M, M = Co, Ni, and Cu) as model catalysts to study the hybrid CO2 electrocatalytic full reaction for the first time, during which the catalysts can simultaneously accomplish photoassisted CO2 electroreduction and 4-nitrophenol (4-NP) mineralization. As model catalysts, the effects of various parameters have been intensively studied from typical tandem electro-reactions to extended photoassisted ones. Specifically, TTCOF-Co can achieve the cathodic reduction efficiency increasing from 90 to 96% (−0.7 V) after illumination and simultaneously 5 times shortened reaction time with a 4-NP degradation efficiency of ∼99%. Notably, the 4-NP mineralization rate is calculated to be ∼93.51% with ∼30.27 mmol/g/h CO2 production rate, and a rarely investigated mechanism relating to the 4-NP electro-degradation has been intensively studied