Controllable Integration and Confinement of Ag Nanoparticles through an Ag Ions‐Coordinated Co‐MOF for Broadband Nonlinear Optical Response

ABSTRACT The discrete electronic energy level structure and surface plasmon resonance effect of metal nanoparticles (MNPs) have great application potential in the field of nonlinear optics, but achieving controllable preparation of the atom count in MNPs remains a major challenge. In this work, the N atoms in Co‐MOF({[Co 1.25 (HL) 0.5 (Pz‐NH 2 ) 0.25 ( µ 3 ‐O) 0.25 ( µ 2 ‐OH) 0.25 (H 2 O)]·0.125Co·0.125L·10.25H 2 O} n , L = 5,5′‐(1H‐2,3,5‐triazole‐1,4‐diyl)diisophthalic acid) were coordinated with Ag + to construct Co‐Ag‐MOF({[Co 1.25 Ag 0.25 L 0.5 (Pz‐NH 2 ) 0.125 ( µ 3 ‐O) 0.25 ( µ 2 ‐OH) 0.25 (H 2 O) 1.75 ]⋅H 2 O⋅CH 3 CN} n ). After reduction treatment, Ag + on the skeleton aggregated in the cavity of Co‐MOF to form atomically controlled Ag nanoparticles (Ag NPs), constructing Ag NPs@Co‐MOF heterogeneous structure. The nonlinear optical (NLO) experimental results conducted under a wide bandwidth indicate that Co‐MOF exhibits saturated absorption (SA), while Co‐Ag‐MOF and Ag NPs@Co‐MOF show reverse saturated absorption (RSA). The RSA signal of Ag NPs@Co‐MOF is stronger than that of Co‐Ag‐MOF. The changes in NLO properties are mainly attributed to the re‐arrangement of energy levels as well as the regulation of electron cloud density between Ag NPs and Co‐MOF. The combined effect of the two factors alters the path of electron transition and the relaxation lifetime of carriers under light excitation. This study achieved the controllable construction of Ag NPs through crystal engineering, offering a novel strategy for the regulation of third‐order NLO properties.