Atomically thin 2D layered transition metal dichalcogenides (TMDs) have been extensively studied in recent years because of their appealing electrical and optical properties. Here, the fabrication of ReS2 field-effect transistors is reported via the encapsulation of ReS2 nanosheets in a high- Al2O3 dielectric environment. Low-temperature transport measurements allow to observe a direct metal-to-insulator transition originating from strong electron-electron interactions. Remarkably, the photodetectors based on ReS2 exhibit gate-tunable photoresponsivity up to 16.14 A W-1 and external quantum efficiency reaching 3168%, showing a competitive device performance to those reported in graphene, MoSe2, GaS, and GaSe-based photodetectors. This study unambiguously distinguishes ReS2 as a new candidate for future applications in electronics and optoelectronics.