硼团簇及其材料化学研究进展(I): 硼墨烯

位于元素周期表中的第五位元素硼, 其丰富的化学结构和多样的成键方式仅次于有机化学和生物科学中的核心元素——碳元素. 硼的缺电子性质导致其必须通过多中心键的方式共享电子以平衡体系的电子分布, 因此硼团簇多具有独特的几何结构和电子离域的成键特性. 近年来, 硼团簇及其材料的研究越来越受到人们的重视, 并取得了一系列研究成果. 通过实验和理论计算, 发现小尺寸的硼团簇多具有平面结构. 2014年, 王来生与李隽两个研究团队合作发现了中心含六元环孔的平面B36−团簇并由此提出了硼墨烯(borophene)概念, 为二维硼材料的发展提供了新的研究方向. 最近中美科学家同时在金属衬底上合成了单层硼墨烯, 使得二维硼材料备受关注. 鉴于硼的缺电子特性, 可以借助于金属掺杂等方式形成各种不同的金属硼化物结构. 具有完美平面结构的CoB18−团簇以及准平面的RhB18−团簇的发现推动了金属掺杂硼墨烯(metallo-borophene)研究的发展. 本文从实验和理论两个方面, 对具有平面或准平面结构的纯硼团簇、金属掺杂硼团簇、二维无限延伸硼墨烯材料等进行了介绍和总结, 并展望了硼团簇二维材料的研究前景和潜在应用. Boron, the fifth element in the period table, exhibits diverse bonding patterns and interesting structures due to its electron deficiency. Unlike its neighbor carbon, closed-packed boron sheet with graphene-like honeycomb lattice is unstable so that planar boron clusters usually have interior vacancies and corrugated appearance. Delocalized multi-center bonding has an important role to stabilize the 2D structures, giving rise to the concept of σ, π, …multiple aromaticity. The experimental observation of the B36− cluster in 2014 established the viability of boron monolayer which was named as “borophene” by Wang and Li. Recently, studies on planar CoB18− and RhB18− clusters have suggested the possibilities of metal-doped borophenes (metallo-borophenes) with potentially tunable electronic, magnetic and optical properties. In this review, we summarize recent experimental and theoretical advances in 2D pure-boron and metal-doped boron clusters, as well as their implications for borophenes and metalloborophenes as novel new boron materials