Reticular chemistry-aided effective design of new second-order nonlinear optical selenites.

Abstract

Noncentrosymmetric (NCS) compounds are particularly important for modern optoelectronic technology, yet their rational structural design remains a great challenge. Herein, assisted by the idea of bottom-up reticular chemistry, seven new NCS selenites, AM3[SeO3]2[Se2O5]3 (A = K+/Rb+/Cs+; M = Al3+/Ga3+/In3+), have been successfully designed and synthesized by assembling main-group metal octahedral units and SeO3 units, to construct honeycomb layers with regular channels to accommodate a variety of cations, and using planar hexagonal shapes to orientate the groups within the network. Based on this strategy, the overall symmetry of the solid-state compounds was effectively controlled, and by modifying locally connected atoms or groups, without disrupting the overall prototypical framework, a series of iso-reticular analogues have been obtained, which greatly increases the probability of NCS structures. Three of these compounds, CsM3[SeO3]2[Se2O5]3 were characterized experimentally and theoretically. The results show that they all have moderate second harmonic generation (SHG) responses, which are as large as that of commercial KH2PO4, and wide band gaps. Our study confirms the feasibility of reticular chemistry-assisted strategy in designing nonlinear optical materials with stable frameworks and good performance.