The physical properties of buckled ZnO monolayers are studied using DFT. It is demonstrated that when the buckling of ZnO monolayers increases, the band gap decreases confirming by both PBEsol and HSE06 approximations. A buckled ZnO monolayer is dynamically and thermally stable as is confirmed by its phonon spectrum and AIMD calculation. If the buckling increases, the frequency ranges for the phonon dispersion decrease resulting in smaller lattice thermal conductivity. Furthermore, a planar ZnO monolayer has an active optical response in the Deep-UV region, however the tunable response reaches the near-UV. Display omitted •Buckling reduces the band gap of ZnO monolayer using PBEsol and HSE06 approximations.•A buckled ZnO monolayer is dynamically and thermally stable.•Buckled ZnO monolayer has an active optical response in the Deep-UV region.•Lattice thermal conductivity is reduced by increasing the buckling parameter.