A visible light responsive nanoporous sulfur doped TiO₂ nanophotocatalyst was prepared by a greener approach using ultrasonic irradiation. The synthesized product was characterized by physicochemical techniques such as X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopy. The elemental composition, morphology and surface area were determined by Energy Dispersive X-ray Spectroscopy (EDXS), Scanning Electron Microscopy (SEM), and High Resolution Transmission Electron Microscopy (HRTEM), Brunauer–Emmett–Teller (BET) surface area analysis, respectively. The results confirmed the formation of a nanoporous S-doped TiO₂ photocatalyst having the anatase phase and exhibiting a particle size of about 8–24 nm. The influence of sulfur doping on the phase transition, band gap and crystalline size of the TiO₂ was investigated by varying the molar ratio of titanium and sulfur. Sulfur doping leads to the lowering of the band gap of TiO₂ from 3.25 eV to 2.47 eV and also delays the phase transition of TiO₂ from the anatase to rutile form. The response of the synthesized catalysts towards the photo-induced degradation of an organic pollutant was investigated in different regions (490 nm, 565 nm and 660 nm) of the solar spectrum using 2-chlorophenol as a model compound. Maximum photocatalytic degradation efficiency was found with S-550 at pH 6 under visible light of 660 nm. The synthesized S-doped TiO₂ photocatalyst showed profound improvement in photocatalytic activity under solar light as compared to TiO₂ Degussa and TiO₂ Merck.