Exploration into the Syntheses of Gallium‐ and Indiumborates under Extreme Conditions: M₅B₁₂O₂₅(OH): Structure, Luminescence, and Surprising Photocatalytic Properties

Abstract

Explorative solid‐state chemistry led to the discovery of the two new compounds Ga5B12O25(OH) and In5B12O25(OH). Extreme synthetic conditions within the range of 12 GPa and a temperature of 1450 °C realized in a Walker‐type multianvil apparatus resulted in the formation of an unprecedented tetragonal structure with the exclusive presence of condensed BO4 tetrahedra, forming cuboctahedral cavities. Doping of these cavities with Eu3+ in In5B12O25(OH) yielded in an orange–red luminescence. Photocatalytic tests of In5B12O25(OH) revealed a hydrogen production rate comparable to TiO2 but completely co‐catalyst free.

Al5B12O25(OH) and Ga4InB12O25(OH) – two additional triel borates with the structure type M 5B12O25(OH) (M = Ga, In)

“…In contrast to Ti 5 B 12 O 26 , where the charge of the missing hydrogen atom is simply compensated by titanium being partially oxidized to 4+, CaMg 2 P 6 O 3 N 10 bears no resemblance regarding the formula at first glance. However, the oxonitridophosphate shows obvious structural similarities which have already been discussed in our original publication of M 5 B 12 O 25 (OH) (M = Ga, In) [1,2].…”

“…In the last decade, our research group focused on highpressure gallium and indium borates represented by 11 different compounds in this field since 2015. Recently, we reported on the successful synthesis of M 5 B 12 O 25 (OH) (M = Ga, In) [1,2], a structure type incorporating either gallium or indium as metal cations. This was an intriguing finding, given that until then only the well-known calcitetype ortho-borates MBO 3 (M = Al, Ga, In, Tl) [3,4] were known to form isotypic compounds in this system.…”

High-pressure synthesis and crystal structure of HP-Al2B3O7(OH)

“…Regarding the system Al-B-O-H, the literature research yields five compounds so far. Besides the well-known mineral Jeremejevite (Al 6 (BO 3 ) 5 (F,OH) 3 ) [1], our working group recently prepared the compound Al 5 B 12 O 25 (OH) which represents a new member of the high-pressure structure type M 5 B 12 O 25 (OH) (M = Al, Ga, In, Ga/In) [2,3]. Jianhua Lin et al who are working on hydrothermally synthesized zeolite-like borate structures, published the remaining three compounds in the system Al-B-O-H.…”

High-pressure synthesis and crystal structure of the mixed-cation borate Ga4In4B15O33(OH)3

“…In the last decade, extensive research has been carried out in the field of group 13 element borates which yielded numerous new structures featuring interesting properties. For instance, triel borates have been reported to show luminescence when being doped with a suitable activator ion [1][2][3][4], and acentric compounds have been described as possible NLO materials [5][6][7]. Especially gallium and indium borates shifted into the research focus due to their photocatalytic properties.…”

“…Especially gallium and indium borates shifted into the research focus due to their photocatalytic properties. During the last 5 years, the results of seven photocatalytic studies of indium or gallium borates have been published [1,[8][9][10][11][12][13]. Up to date, 14 borates are known in the systems Ga-B-O(-H) and In-B-O(-H), from which 12 have been published since 2010.…”