Mild acid functionalization of metal-organic framework and its catalytic effect on esterification of acetic acid with n-butanol

•The mild functionalization method successfully introduces BrÖnsted acidity to the NH2-MIL-101(Al), without any significant structural degradation.•S-MIL-101, as a BrÖnsted acidic heterogeneous catalyst, exhibited 66% acetic acid conversion at 70 ℃.•S-MIL-101 showed better acidic conversion than the four existing acid MOF catalysts including HSO3-MIL-101(Cr)HCl, HSO3-MIL-101(Cr)HF, HSO3-UiO-66(Zr),and HSO3-MIL-53(Al).•The performance of S-MIL-101 was comparable to commercial Amberlyst-15 and Nafion NR-50.