<p>Metal-organic frameworks (MOFs) are promising membrane materials for molecular separations because of their well-defined porosity and tunable chemistry. However, their separation performance is often limited by grain boundaries and interfacial defects that introduce non-selective transport pathways. Here, we proposed an in-situ interfacial polyesterification-assisted bonding strategy for constructing MOF-rich self-standing membranes using triethanolamine (TEOA) in the UiO-66 system. Under thermal treatment, TEOA is proposed to induce localized interfacial reactions that generate anchored polyester species at MOF-MOF contacts, thereby enhancing particle bonding and suppressing non-selective interface defects. The resulting UiO-66 polyester membrane exhibits 92.7 wt% UiO-66 loading, a CO₂ permeance of 1310 GPU, and a CO₂/N₂ selectivity of 38, surpassing the upper bound for this gas pair, with the selectivity arising primarily from solubility-selective transport. In addition, the UiO-66 polyester membrane shows good moisture tolerance and performance regenerability, further suggesting that the polyesterified interface helped mitigate humidity-induced interfacial deterioration and suppress particle-interface defects. A similar strategy is also demonstrated in the MOF-808, UiO-67, and MIL-101 systems, indicating representative applicability within a subset of carboxylate-based MOFs. These results highlight the importance of interfacial chemical engineering in constructing defect-suppressed, highly MOF-rich separation membranes.</p>