Instant One‐Pot Preparation of Functional Layered Double Hydroxides (LDHs) via a Continuous Hydrothermal Approach

Abstract

International audienceInstant one-pot synthesis of functional layered double hydroxides (LDHs) is demonstrated for the first time using a continuous hydrothermal multi-step process. The as-prepared pristine material displays high crystallinity and very small LDH nanoparticle size, lateral dimensions below 100 nm and a thickness below 20 nm, all being achieved in only 5 s. This approach was extended to the preparation of i) pristine LDH with different compositions by varying the cation (Mg, Ni, or Zn) and the anion (CO3, NO3) and ii) functional LDH by varying the functionalization agent, for example long organic molecules (hybrid LDH), enzymes (bio-hybrid LDH) or inorganic metal/oxide nanocrystals (inorganic-LDH). Beyond the design of functional LDH, this paper presents proof of concept for a continuous, one-pot and multistep high temperature/high pressure (HT/HP) process for the assembly of nanoscaled materials

Synthesis of layered double hydroxides through continuous flow processes: A review

“…In spite of the great interest of functional LDH and LDH-based composites for several industrial applications, their synthesis has been still scarcely investigated through continuous flow methods. However, since 2015 functionalization of LDH with enzymes, surfactants or nanoparticles has been emerging [126][127][128]. Noteworthy, in these recent reports the biohybrids are likely formed by immobilization of the enzymes on the LDH nanoparticles, whereas the organic-LDH hybrids are obtained either by intercalation or by immobilization of surfactants on the surface.…”

“…O. Pascu et al have achieved the one-pot synthesis in a continuous hydrothermal multi-step process of functional LDHs intercalated by large organic species like dodecyl sulfate (DS), with immobilized enzymes (i. e. transketolase (TK)) and deposited metal/oxide nanocrystals (Pd orRu NCs). Thus they obtained organic-hybrids, bio-hybrid and inorganic LDH in a highly versatile method[128]. The process uses a configured set-up directly inspired from a supercritical microfluidic co-flow system previously used for the synthesis of hybrid ZnO or Pd nanocrystals[135,136].…”

“…Figure23: Sketch of the continuous hydrothermal synthesis approach for the synthesis in onepot of functionalized LDHs (Reproduced with permission from Ref [128]…”

Chemistry in supercritical fluids for the synthesis of metal nanomaterials

“…Near-/supercritical H2O is one of the most investigated fluids for the synthesis of multiple types of nanomaterials, ranging from oxides, 53,[140][141][142][143][144] minerals, layered double hydroxides, 57,58,145,146 sulphides, 147 to metalorganic frameworks. 148 H2O is readily available, and especially by combining it with the flow chemistry process a high-throughput scalable way of synthesis is obtained, the so-called supercritical hydrothermal flow synthesis.…”

Continuous Hydrothermal Flow Synthesis of Co1–xNixFe2O4 (x = 0–0.8) Nanoparticles and Their Catalytic Properties for CO Oxidation and Oxygen Evolution Reaction

“…As a result, a high degree of supersaturation is achieved and nucleation starts almost instantaneously upon mixing. To date, various types of nanomaterials prepared by CHFS have been reported, including oxides, metals, sulfides, metal organic frameworks (MOFs), layered double hydroxides, and minerals , . In addition, upscaled operations at industrial level have been proven at pilot scale, in a full commercial plant (Hanwha Chemical Corp., Republic of Korea), and in the European FP7 project SHYMAN (http://www.shyman.eu).…”