Modulation of Third-Order Nonlinear Optical Properties by Interfacial Interactions of Defected Bimetallic-MOF@CeO₂

MOF@CeO₂ composites with good interfacial compatibility have garnered significant attention in the field of third-order nonlinear optics (NLO). However, the interfacial interaction between the MOFs and CeO₂ is commonly weak, which severely weakens the third-order NLO properties of the composites. In this study, we chose the parent Zn-MOF ({[Zn(BPAN)_0.5(ndcpa)]·DMA·H₂O}) (BPAN = 9,10-bis(4-pyridyl)anthracene and H₂ndcpa = naphthalene-2,6-dicarboxylicacid) and synthesized bimetallic-MOFs (ZnNi-MOF and ZnCo-MOF) by solvent-assisted metal-ion exchange. The defect sites originating from the exchange make the interface interaction of bimetallic-MOF@CeO₂ composites (ZnNi-MOF@CeO₂ and ZnCo-MOF@CeO₂) stronger. The third-order NLO results indicate bimetallic-MOF@CeO₂ composites display enhanced reverse saturable absorption and self-defocusing refraction properties compared to Zn-MOF@CeO₂, which can be attributed to efficient charge transfer at interfaces. Transient absorption spectra and theoretical calculation revealed that good interfacial compatibility significantly reduced interfacial energy loss, enhanced electron transfer efficiency, and positively modulated the third-order NLO properties. This study provides new insights and methodologies for the design and development of novel third-order NLO composites.