Understanding thermal transport in nanostructured materials is important for the development of energy conversion applications(1-4) and the thermal management of microelectronic and optoelectronic devices(5). Most nanostructures interact through van der Waals interactions(6), and these interactions typically lead to a reduction in thermal transport(7-10). Here, we show that the thermal conductivity of a bundle of boron nanoribbons can be significantly higher than that of a single freestanding nanoribbon. Moreover, the thermal conductivity of the bundle can be switched between the enhanced values and that of a single nanoribbon by wetting the van der Waals interface between the nanoribbons with various solutions.