Co anchored on porphyrinic triazine-based frameworks with excellent biocompatibility for conversion of CO_(2)in H_(2)-mediated microbial electrosynthesis

Microbial electrosynthesis is a promising alternative to directly convert CO_(2)into long-chain compounds by coupling inorganic electrocatalysis with biosynthetic systems.However,problems arose that the conventional electrocatalysts for hydrogen evolution may produce extensive by-products of reactive oxygen species and cause severe metal leaching,both of which induce strong toxicity toward microorganisms.Moreover,poor stability of electrocatalysts cannot be qualified for long-term operation.These problems may result in poor biocompatibility between electrocatalysts and microorganisms.To solve the bottleneck problem,Co anchored on porphyrinic triazine-based frameworks was synthesized as the electrocatalyst for hydrogen evolution and further coupled with Cupriavidus necator H16.It showed high selectivity for a four-electron pathway of oxygen reduction reaction and low production of reactive oxygen species,owing to the synergistic effect of Co–Nx modulating the charge distribution and adsorption energy of intermediates.Additionally,low metal leaching and excellent stability were observed,which may be attributed to low content of Co and the stabilizing effect of metalloporphyrins.Hence,the electrocatalyst exhibited excellent biocompatibility.Finally,the microbial electrosynthesis system equipped with the electrocatalyst successfully converted CO_(2)to poly-β-hydroxybutyrate.This work drew up a novel strategy for enhancing the biocompatibility of electrocatalysts in microbial electrosynthesis system.

Room-temperature hydrogenation of halogenated nitrobenzenes over metal-organic-framework-derived ultra-dispersed Ni stabilized by N-doped carbon nanoneedles

Ultra-dispersed Ni nanoparticles(7.5 nm)on nitrogen-doped carbon nanoneedles(Ni@NCNs)were prepared by simple pyrolysis of Ni-based metal–organic-framework for selective hydrogenation of halogenated nitrobenzenes to corresponding anilines.Two different crystallization methods(stirring and static)were compared and the optimal pyrolysis temperature was explored.Ni@NCNs were systematically characterized by wide analytical techniques.In the hydrogenation of p-chloronitrobenzene,Ni@NCNs-600(pyrolyzed at 600°C)exhibited extraordinarily high performance with 77.9 h^(–1)catalytic productivity and>99%p-chloroaniline selectivity at full p-chloronitrobenzene conversion under mild conditions(90°C,1.5 MPa H2),showing obvious superiority compared with reported Ni-based catalysts.Notably,the reaction smoothly proceeded at room temperature with full conversion and>99%selectivity.Moreover,Ni@NCNs-600 afforded good tolerance to various nitroarenes substituted by sensitive groups(halogen,nitrile,keto,carboxylic,etc.),and could be easily recycled by magnetic separation and reused for 5 times without deactivation.The adsorption tests showed that the preferential adsorption of–NO2 on the catalyst can restrain the dehalogenation of p-chloronitrobenzene,thus achieving high p-chloroaniline selectivity.While the high activity can be attributed to high Ni dispersion,special morphology,and rich pore structure of the catalyst.