【摘要】 合理设计并制备新型氮化碳是化学和材料领域的研究热点.本文受尿素聚合的启发,以草酰二胺替代部分尿素制备了C-C桥联、结构接近C₆N₇的新型氮化碳UO_x（x为尿素与草酰二胺的物质的量之比, x=1、1.5、2、2.5和3）.密度泛函理论计算表明, UO_x的共轭性由单个庚嗪环扩展到了整个材料框架.因此,其禁带宽度缩小到2.05 e V,吸收带边被大幅扩展到600 nm.此外,它的载流子传输和分离也得到显著增强,因而展现出优异的光催化活性.在一系列样品中, UO₂具有最佳的光催化活性,其光催化析氢速率约为108.59μmol h^-1 （10mg催化剂）,表观量子效率在420和600 nm下分别为36.12%和0.33%.此外, UO₂对二苯肼氧化以及酚类降解也呈现明显优于传统g-C₃N₄的优异光催化活性和稳定性,它是一类极具发展前景的新型二维材料.更多还原

【Abstract】 The rational design and construction of novel two-dimensional（2 D） carbon nitrides（CNs） beyond g-C₃ N₄ is a hot topic in the fields of chemistry and materials. Inspired by the polymerisation of urea, we have prepared a series of novel C–C bridged heptazine CNs UO_x（where x is the ratio of urea to oxamide,x = 1, 1.5, 2, 2.5, and 3）, which are similar to（C₆ N₇）n, upon the introduction of oxamide. As predicted using density functional theory（DFT） calculations, the conjugated structure of UO_xwas effectively extended from an individual heptazine to the entire material. Consequently, its bandgap was reduced to 2.05 e V,and its absorption band edge was significantly extended to 600 nm. Furthermore, its carrier transfer and separation were significantly enhanced, establishing its superior photocatalytic activity. The optimised UO₂ exhibits a superior photocatalytic hydrogen production rate about 108.59 lmol h^-（1）（using10 mg of catalyst） with an apparent quantum efficiency（AQE） of 36.12% and 0.33% at 420 and600 nm, respectively, which is one of the most active novel CNs reported to date. Moreover, UO₂ exhibits excellent photocatalytic activity toward the oxidation of diphenylhydrazine to azobenzene with conversion and selectivity reaching ～100%, which represents a promising highly efficient 2 D CN material.Regarding phenols degradation, UO₂ also displayed significantly higher activity and durability during the degradation of phenol when compared to traditional g-C₃ N₄, highlighting its significant potential for application in energy, environment and photocatalytic organic reactions.更多还原