Direct molecular confinement in layered double hydroxides: from fundamental to advanced photo-luminescent hybrid materials

Two-dimensional organic-inorganic hybrid materials based on layered double hydroxides (LDHs) have drawn significant attention during the last decade. The development of such materials is usually based on the intercalation of LDHs. However, the direct intercalation of organic guest molecules into the gallery of LDHs using carbonate-intercalated LDHs as the starting material is still challenging. To this end, we propose here a new approach with general applicability in the efficient de-carbonation and direct intercalation of LDHs using organic acids. The intercalation mechanism has been investigated in detail using acetic acid as a proof of concept. It is demonstrated that the interlayer carbonates of LDHs are converted into carbon dioxides in the presence of acetic acid, thus leaving acetates as counter-anions within the gallery of LDHs. The feasibility of the methods has been examined using LDHs of different lateral sizes and layer compositions. As a result, various aliphatic and aromatic organic anions including carboxylates, sulfonates and phosphonates have been successfully intercalated into the galleries of LDHs. Moreover, aggregation-induced emission molecules have also been intercalated into LDHs to develop a new type of photo-luminescent hybrid material that exhibits enhanced fluorescence and quantum yield. Therefore, this work provides a new approach for the facile preparation of LDH hybrids and design of hybrid materials for applications in diverse fields such as energy, the environment, medicine, and catalysis. We report here new approaches for the direct intercalation of layered double hydroxides (LDHs) from carbonate-LDHs by using various organic acids as proton sources for de-carbonation.