A Dual-Purpose Ce(III)-Organic Framework with Amine Groups and Open Metal Sites: Third-Order Nonlinear Optical Activity and Catalytic CO₂ Fixation

The present work focuses on the synthesis and propertiesof a novelmultifunctional cerium(III) MOF, [Ce-2(data)(3)(DMF)(4)]& BULL;DMF (data(2-): 2,5-diaminoterephthalate),abbreviated as NH2-Ce-MUM-2. Its crystal structure revealsan intricate 3D 4,5-connected framework with a xah topology.This MOF features unique properties, such as open metal sites, presenceof free amino groups, and high stability. Two main applications ofNH(2)-Ce-MUM-2 were investigated: (i) as a heterogeneouscatalyst in the CO2 fixation into cyclic carbonates and(ii) as a material with third-order nonlinear optical activity. Asa model reaction, the cycloaddition of CO2 to propyleneoxide to give the corresponding cyclic carbonate was explored undermild conditions, at the atmospheric pressure of carbon dioxide andin the absence of cocatalyst and added solvent. Various reaction parameterswere investigated toward optimization and exploration of substratescope, revealing up to 99% product yields of cyclic carbonate products.Besides, the structure of NH2-Ce-MUM-2 is highly stable,permitting its recyclability and reusability in further catalyticexperiments. The significant contributions of free amino groups andopen metal sites within this catalyst were particularly consideredwhen proposing a potential mechanism for the reaction. Z-Scan measurements were used to evaluate the nonlinear optical (NLO)properties of NH2-Ce-MUM-2 at various laser intensities.A high two-photon absorption (TPA) under greater incident intensitiesshows that NH2-Ce-MUM-2 might be applicable in opticalswitching devices. Besides, the self-focusing effects of NH2-Ce-MUM-2 under various incident intensities were highlighted bythe nonlinear index of refraction (n (2)).By reporting the synthesis and characterization of a novel MOF, alongwith its highly promising catalytic and NLO behavior, the currentstudy introduces an additional example of multifunctional materialinto a growing family of metal-organic frameworks.