Cation regulation achieves symmetry breaking: from centrosymmetric M 2 Cs 2 B 10 O 17 (M = Na, K) to noncentrosymmetric Na 3 CsB 10 O 17

A new NCS borate, Na 3 CsB 10 O 17 , was synthesized via cation regulation in Na 2 Cs 2 B 10 O 17 . It achieves symmetry breaking (CS→NCS) in the 2 [B 10 O 17 ] ∞ framework and exhibits a DUV cutoff edge <190 nm. This work establishing a design paradigm for NCS borates.