The photodimerization of 2-naphthalenecarbonitrile (2-NpCN) in a cucurbit[8]uril (CB[8]) aqueous solution was investigated. Spectroscopic analysis and product distribution reveal that the use of CB[8] as a host inverted the product selectivity from photodimers 2 and 3 in cyclohexane to photodimer 1 in a CB[8] aqueous solution with a large rate acceleration under ambient temperature and pressure.
![Graphical abstract: Efficient and selective photodimerization of 2-naphthalenecarbonitrile mediated by cucurbit[8]uril in an aqueous solution](http://hg.y866.cn/compound/lib/scimg/usr/1/C1PP05047H.jpg)
