Metal Cations as Inorganic Structure-Directing Agents for the Preparation of Zeotype Aluminosilicates (Case No. 2022-246)

Summary

UCLA researchers have developed a method for directing the crystallization of aluminosilicate materials into either phillipsite zeolite or tobermorite silicate hydrate phases—using specific ratios of sodium (Na⁺), potassium (K⁺), and calcium (Ca²⁺) cations in synthesis gels, without organic structure-directing agents (OSDAs).

Background

Zeolites (like phillipsite) and silicate hydrate minerals (like tobermorite) are highly useful for adsorption, ion exchange, catalysis, building materials, and potentially in cementitious or environmental applications. Standard synthesis of zeolites often relies on organic templates (OSDAs), which are expensive, environmentally burdensome, and complicate scale-up. There is a need for simpler, greener synthetic methods that allow tunable control over material phase (zeolite vs silicate hydrate), porosity, and composition.

Innovation

This technology defines hydrothermal synthesis gels composed of Al, Si, H₂O, and varying mixtures of Na⁺, K⁺, and Ca²⁺. By adjusting the charge ratio of calcium relative to total cationic charge (via ((2×Ca²⁺)/(Na⁺ + K⁺ + 2×Ca²⁺))) and by selecting treatment temperature (e.g. ~373 K or 393 K), the process controls whether phillipsite dominates (when Na and K are present and Ca content is low) or tobermorite predominates (when Ca is high and Na/K are reduced/absent). Key features: no organic templates needed, capability for mixed‐phase materials, controllable micropore volumes (on the order of 0.001-0.1 cm³/g), and use of well-understood metal cations both as aluminum counterbalance and as structure directors.

Advantages

• Eliminates the need for organic structure-directing agents, simplifying and lowering the cost and environmental impact of synthesis.

• Enables selective formation of either zeolite (phillipsite) or silicate hydrate (tobermorite) by adjusting cation composition and synthesis temperature.

• Tunable porosity and crystal morphology (micropore volume, cavity structure) via synthesis parameters.

• Uses common, inexpensive metal cations (Na, K, Ca), avoiding exotic chemicals.

• Potentially scalable via hydrothermal protocols under moderate temperatures.

• Flexibility to produce mixed-phase materials if desired, which may combine favorable properties of both phases.

Potential Applications

• Zeolites for ion exchange, water purification, or pollutant capture materials.

• Silicate hydrate phases (tobermorite) for cementitious or binding applications, possibly improving durability, strength, or reducing CO₂ footprint.

• Catalytic supports or adsorbents where controlled microporosity and framework topology matter.

• Building materials or composites where mixed phases with tuned porosity are beneficial.

• Environmental remediation, filtration, or separations (e.g. heavy metals, ammonia, etc.).

Patent / Application

US 2023/0391631 A1 — Metal cations as inorganic structure-directing agents during the synthesis of phillipsite and tobermorite
Priority Date: May 23, 2022; Application Filed: May 23, 2023; Publication Date: December 7, 2023.
Metal cations as inorganic structure-directing agents during the synthesis of phillipsite and tobermorite (US20230391631A1)

Publications by the Inventors (Related Work)

• Vega-Vila, J. C.; Holkar, A.; Arnold, R. A.; Prentice, D. P.; Dong, S.; Tang, L.; La Plante, E. C.; Ellison, K.; Kumar, A.; Bauchy, M.; Srivastava, S.; Sant, G.; Simonetti, D. Metal cations as inorganic structure-directing agents during the synthesis of phillipsite and tobermorite. Reaction Chemistry & Engineering, 2023, 8(5), 1176-1184. DOI: