Regulation of Third‐Order NLO Properties by Central Metal Exchange of Heterogeneous MOFs@CeO₂

Abstract Changing the chemical composition and generating heterogeneous structures have a synergistic effect on the third‐order nonlinear optical (NLO) properties of metal–organic frameworks (MOFs) materials. In this work, it is demonstrated that the transformations from a parent‐MOF [Zn₄(dcpp)₂(DMF)₃(H₂O)₂]_n (1, dcpp = 3,4‐bis(4‐carboxyphenyl)phthalate) into two child‐MOFs, [Cu₄(dcpp)₂(DMF)₃(H₂O)₂]_n (2) or [Zn_2.5Co_1.5(dcpp)₂(DMF)₃(H₂O)₂]_n (3), via central metal exchange can regulate the third‐order NLO properties of the parent‐MOF, especially its third‐order NLO absorption signal can change from the reverse saturable absorption (RSA) to the saturable absorption (SA) when Cu²⁺ are introduced. Heterogeneous 1@CeO₂ materials are further engineered by depositing CeO₂ nanospheres onto the whole surface of 1, and are surprisingly still able to be exchanged into 2@CeO₂ or 3@CeO₂. Analyses on these MOFs@CeO₂ indicate that the interfacial interaction between metal oxide particles and MOFs surface can effectively tune the charge transfer efficiency of the material which leads to their third‐order NLO refraction signals. The interface inducement of CeO₂‐shell to the MOF‐core also significantly changes their third‐order NLO properties compared to pure MOFs. This work provides new insights and efficient strategies for the development of new third‐order NLO materials with potential practical usage.