Post‐Synthetic Modification of Zr‐Metal–Organic Frameworks through Cycloaddition Reactions

Cycloaddition reactions are highly attractive for post‐synthetic modification of metal–organic frameworks (MOFs). We report herein on cycloaddition reactions with PIZOF(R 1 ,R 2 )s, which are porous interpenetrated Zr‐based MOFs with Zr 6 O 4 (OH) 4 (CO 2 ) 12 as the nodes and the dicarboxylates − O 2 C[PE‐P(R 1 ,R 2 )‐EP]CO 2 − (P: phenylene, E: ethynylene; R 1 , R 2 : side chains at the central phenylene unit) as the linkers. 1,3‐Dipolar cycloaddition between the pendant ethyne moieties of PIZOF(OMe,OCH 2 CCH) and 4‐methylbenzyl azide resulted in 98 % conversion of the ethyne groups. Reactions of PIZOF(OMe,O(CH 2 ) 3 furan) with maleimide, N ‐methylmaleimide, and N ‐phenylmaleimide converted 98, 99, and 89 % of the furan moieties into the Diels–Alder adducts. However, no reaction occurred with maleic anhydride. High‐resolution 1 H NMR spectra were crucial in determining the conversion and identifying the reaction products. Of all the reagents (NaOD/D 2 O, D 2 SO 4 , Bu 4 NF, CsF, CsF/DCl, and KHF 2 ) tested for the disassembly of the PIZOFs in [D 6 ]DMSO, the combination of CsF and DCl was found to be the best. The disassembly at room temperature was fast (5–15 min), and after the addition of K 2 CO 3 the 1 H NMR data were identical to those of the diacids (=protonated linkers) dissolved in pure DMSO. This allowed for simple structure elucidation through data comparison. CsF/DCl dissolves not only PIZOFs but also the hydrolytically very stable UiO‐66.