Steric and solvent effects on epoxide reactivity in post-synthetic modification of UiO-66-NH2

Post-synthetic modification (PSM) of amine-functionalized MOFs offers a powerful strategy for diversifying pore chemistry without altering the underlying framework structure. Here, we systematically investigate the influence of epoxide size, solvent environment, and reagent concentration on the reactivity and structural effects of epoxide-based PSM in UiO-66-NH 2 . Using a series of electrophiles, 1,2-ethylene oxide (EE), 1,2-propylene oxide (EP), and 1,2-epoxybutane (EB) with increasing steric hindrance, we compare reactions performed in aprotic (THF) and protic (H 2 O) systems using combined PXRD, N 2 sorption, NMR, and HPLC-MS-DAD analyses. Reactions in THF proceed via selective aminolysis, forming β-hydroxylalkylamino with limited reduction in porosity. In contrast, a protic system leads to epoxide hydrolysis as a side reaction, which accumulates in the pores and reduces the accessible surface area. Concentration-dependent studies with EB further reveal how steric crowding and hydrolytic pathways amplify pore obstruction. Across all conditions, the UiO-66 framework remains structurally robust, but the extent of pore accessibility and product heterogeneity correlates strongly with epoxide size and solvent environment. These structural properties and reactivity trends define how pore chemistry and accessibility can be tuned through selective epoxide design.