Turning Flexibility into Rigidity: Stepwise Locking of Interpenetrating Networks in a MOF Crystal through Click Reaction

Post-synthetic modifications of metal–organic frameworks (MOFs) enable synthesis materials with enhanced performance characteristics or those inaccessible by direct synthetic routes. In this work, for the first time, we utilize inverse-electron demand Diels–Alder (iEDDA) modification to control structural flexibility and porosity an open framework material. We selected a series dienophiles increasing bulkiness including ethyl vinyl ether (eve), cyclohexene (chx), norbornene (nor), 5-norbornene-2-methanol (noh) modify tetrazine-based linker (3,6-dipyridyl-1,2,4,5-tetrazine, dpt) incorporated in unique doubly interpenetrated 3D hybrid MOF–HOF porous material (HOF, hydrogen-bonded organic framework), {[Cd2(coh)2(dpt)2]·guests}n (JUK-20). Each subnetwork JUK-20 is built 2D coordination layers stacked strong complementary C?O···H–N hydrogen bonds between carbohydrazide dibenzoate linkers (coh). By using [4 + 2] click reactions JUK-20, which proceed prominent single-crystal-to-single-crystal manner, obtained JUK-20-dienophile MOFs. The lead stepwise decrease platform until highest rigidity stability reached JUK-20-noh. Consequently, adsorption capacity increases, as revealed collectively single-crystal X-ray diffraction, physisorption isotherms (N2, CO2, MeOH), grand canonical Monte Carlo simulations. Our work demonstrates that post-synthetic iEDDA versatile efficient tool systematic functionalization under mild conditions.