Few-layer graphitic carbon nitride (g-C3N4) nanosheets with holey porous structures were prepared by fast treatment bulk g-C3N4 using environmental-friendly flash frozen exfoliation method within several seconds. The products were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and electrochemical impedance spectroscopy. The foam-like holey ultrathin g-C3N4 nanosheets exhibit high crystallinity, narrower band gap (2.46 eV), more exposed edges and enhanced electron transport ability. N-2 adsorption desorption tests show that the few-layer g-C3N4 has a slightly-enlarged specific surface area of 135.6 m(2)/g and enriched small mesopores. Compared with bulk g-C3N4, the few-layer holey g-C3N4 showed a significantly enhanced ability of reactive oxygen species generation and 4-fold higher activity for visible light -driven Rhodamine B photodegradation, which were mainly attributed to the enriched active sites and shorter pathway from the carrier to the reaction sites. These findings provide an inspiration for clean scale-up production of highly-active few-layer g-C3N4 pholocatalysts towards environmental and biological applications. (C) 2017 Elsevier B.V. All rights reserved.