Synthesis And Catalytic Performance Of Cobalt-based Composite Materials Derived From Nitrogen-Silica-Doped Carbon

Chemical industry plays an important role in the process of human society,and catalysts constitute a vital position in chemical industry,over 85%industrial processes involve the use of catalysts.In recent years,supported catalysts,especially nitrogen-doped carbon materials have been widely applied in the field of energy-related,fine chemistry and bulk chemistry,and further improvement of catalytic activity and selectivity of supported catalysts is the key to solve environmental issues and improve productivity.Hence,it is of significant importance in both theory and practice to develop novel efficient,selective and low cost carbon supported catalysts.The incorporation of nitrogen atoms into the catalysts can influence the properties of the support and the supported metal nanoparticles in several ways.It can enhance the interaction between metal and support,narrow the size of nanoparticles,stable the nanoparticles and prevent them from agglomeration in the process of reaction,moreover,the doped nitrogen can improve the wettability in polar solution,thus improving the catalytic activity in the reaction.The introduction of silica can modify the micropore size of support,enhance its mechanical stability,thus favoring the mass transfer and catalytic activity.In this paper,we synthesized three kinds of cobalt-based nitrogen-silica-doped carbon catalysts derived from commercially available carbon materials as carbon source,and applied them into dehydrogenative coupling of?Hetero?aryl-fused 2-Alkylcyclic Amines and Aldehydes,oxidative esterification of thiols and alcohols with alcohols and reversible dehydrogenation and hydrogenation of N-heterocycles,respectively.The details are as follows:?1?By developing a low-loading cobalt-based nanocatalyst with nitrogen-silica-doped carbon?Vulcan XC-72R?as the support?Co/N-Si-C?,we have demonstrated a dehydrogenative coupling of?hetero?aryl-fused 2-alkylcyclic amines with aldehydes to give?E?-2-alkenylazaarenes for the first time.In the reaction,effective capture of the partially dehydrogenated cyclic amine motifs appears to be a key strategy to address the chemoselective issue.The developed chemistry proceeds with the merits of broad substrate scope,excellent functional group tolerance,high atom-efficiency,use of an earth-abundant and reusable cobalt catalyst and molecular O₂ as a green oxidant,which offers an important basis for direct conversion of inert cyclic amine units into the functional frameworks.?2?By developing a cobalt nanocatalyst supported on N-SiO₂-doped activated carbon,which exhibits excellent catalytic performance towards the oxidative esterification of aryl,heteroaryl,alkyl thiols and alcohols with alcohols in the presence of O₂ and K₂CO₃.A wide array of sulfinic esters and esters were efficiently afforded in an exclusive chemoselective manner.The developed synthetic protocol proceeds with merits of mile reaction conditions,broad substrate scope,operational simplicity,good functional group tolerance,high atom-efficiency,earth-abundant and reusable cobalt catalyst,the utilization of renewable alcohols as coupling partners and molecular O₂ as the sole oxidant,which offers a practical way for sustainable synthesis of sulfinic esters and esters.?3?Nitrogen-silica-doped carbon nanotubes supported cobalt catalysts are prepared to catalyze reversible dehydrogenation and hydrogenation of N-heterocycles.In the hydrogenation reaction,ammonia borane was chosen to be hydrogen source to perform the hydrogenation of series of N-heterocycles and cobalt-nitrogen was proved to be the active species.In addition,the same catalytic materials were applied to perform the dehydrogenation of N-heterocycles under mild conditions.In both hydrogenation and dehydrogenation of N-heterocycles,the catalysts showed excellent catalytic performance and good stability.