Thanks to its tunable direct band gap, high charge-carrier mobility, and unique in-plane anisotropic structure, black phosphorus (BP) has become a rising star among post-graphene two-dimensional (2D) nanomaterials. However, BP is unstable under ambient conditions, which largely limits its application. In this paper, an organosilicon agent, TMSCl, was used for the surface coordination of BP nanosheets to generate TMSCl@BP, which could maintain its surface morphology and properties for 24 h under ambient conditions and has no cytotoxicity at a concentration of 200 ppm as per previous reports. Our study is the first evidence that bare BP can coordinate with organosilicon to generate the more stable TMSCl@BP. Notably, the photothermal effect of TMSCl@BP was maintained after exposure to ambient conditions for over 24 hours.