Lewis acid dilution suppresses non-radiative recombination in near-infrared-responsive tin poly(heptazine imide) photocatalysis

A novel near-infrared-responsive Sn-PHI has been developed. • Revealing the microscopic mechanism of the Lewis acid dilution effect for the first time. • Breaking the trade-off between broad spectrum absorption and high crystallinity. Tin poly(heptazine imide) shows superior light absorption over traditional alkali/alkaline earth metal counterparts. Tin(II) chloride (SnCl 2 ) is a convenient tin source but its strong Lewis acidity introduces structural defects that cause non-radiative recombination of photogenerated carriers. To address this issue, we dilute the Lewis acidity of SnCl 2 using five types of chloride salts. Taking LiCl as an example, molecular dynamics simulations confirm that the introduction of LiCl transforms the coordination environment of Sn 2 + from N-dominated to Cl - -dominated, reducing the Sn–N coordination number, thereby validating the Lewis acidity dilution effect. Experimentally, appropriate LiCl addition buffers SnCl 2 Lewis acidity, suppresses excessive and deep nitrogen vacancies, and thus significantly suppresses non-radiative recombination. This Lewis acidity dilution strategy resolves the contradiction between framework integrity and broadband light absorption, paving the way for novel crystalline carbon nitride photocatalysts with broad-spectrum response. Download: Download high-res image (127KB) Download: Download full-size image