Robust Fluorine-Functionalized {Ln5}-Organic Frameworks for Excellent Catalytic Performance on Cycloaddition of CO2 with Epoxides and Knoevenagel Condensation

Lanthanide-organic frameworks (LnOFs) are a classof promisingcatalysts on a large number of organic reactions because of the highercoordination number of Ln(3+) ions, inspired by which exploratorypreparation of cluster-based LnOFs was carried out by us. Herein,the exquisite combination of spindly [Ln(5)(& mu;(3)-OH)(6)(CO2)(6)(H2O)(6)] clusters (abbreviated as {Ln(5)}) and fluorine-functionalizedtetratopic ligand of 2 & PRIME;,3 & PRIME;-difluoro-[p-terphenyl]-3,3 & DPRIME;,5,5 & DPRIME;-tetracarboxylic acid (F-H(4)PTTA) engendered two highly robust isomorphic nanoporous frameworksof {[Ln(5)(FPTTA)(2)(& mu;(3)-OH)(6)(H2O)(6)](NO3)}( n ) (NUC-61, Ln = Ho and Dy). NUC-61 compounds are rarely reported{Ln(5)}-based 3D frameworks with nano-caged voids (19 & ANGS;x 17 & ANGS;), which are shaped by twelve [Ln(5)(& mu;(3)-OH)(6)(COO)(8)] clusters and eight completelydeprotonated F-PTTA(4-) ligands. Activated NUC-61a compounds are characterized by plentiful coexisted Lewis acid-basesites of open Ln(III) sites, capped & mu;(3)-OH,and -F. Judged by the ideal adsorbed solution theory (IAST), activated NUC-61Ho-a had a high CO2/CH4 adsorptiveselectivity with the value of 12.7 (CO2/CH4 =50/50) and 9.1 (CO2/CH4 = 5/95) at 298 K, whichcould lead to high-purity CH4 (& GE;99.9996%). Furthermore,catalytic experiments exhibited that NUC-61Ho-a, as arepresentative, could efficiently catalyze the cycloaddition reactionsof CO2 with epoxides as well as the Knoevenagel condensationreactions of aldehydes and malononitrile. This work proves that the{Ln(5)}-based skeletons of NUC-61 with chemicalstability, heterogeneity, and recyclability are an excellent acid-basebifunctional catalyst for some organic reactions.