Two-dimensional χ_eff – q histograms of BH–BH merger rate density $\frac{\mathrm{d}{R}_{\mathrm{BHBH}}}{\mathrm{d}q\mathrm{d}{\chi }_{\mathrm{eff}}}$[Gpc⁻³yr⁻¹] up to redshifts z_mer < 1.0 in our default model with the revised mass transfer stability criteria (Pavlovskii et al. 2017; Olejak et al. 2021). The BH–BH mergers have been produced via SMT (black and blue colors) and CE (green and red colors) subchannels. The formation of highly spinning mergers with χ_eff ⪆ 0.15 was followed by a tidal spin-up phase in close BH-helium core binaries (blue and red colors).