Phenothiazine Schiff Base Catalysts Against Metal Self-Polymerization

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Solution Overview

Problem

The Lewis acidic metal center of metal Schiff base complexes is prone to self-polymerize during catalytic reactions, leading to inactivation and reduced activity and stability of the catalysts used for synthesizing cyclic carbonates.

Innovation Solution

A phenothiazine metal Schiff base catalyst is developed, which forms phenothiazine free radicals to protect the central metal, inhibiting self-polymerization and enhancing catalyst stability and activity, allowing efficient synthesis of cyclic carbonates under mild conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If metal Schiff base complex is used as catalyst for cyclic carbonate synthesis, then catalytic activity is improved, but self-polymerization of metal center occurs leading to reduced stability

Engineering Contradiction:

Improvecatalytic activityVSAvoidcatalyst stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent creates a composite catalyst system by combining metal Schiff base complex with phenothiazine compound. The phenothiazine acts as a stabilizing component that prevents self-polymerization of the metal center while maintaining catalytic activity. This composite approach allows the catalyst to simultaneously achieve high productivity and reliability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The phenothiazine compound serves as an intermediary substance that mediates between the metal center and the reaction environment. It coordinates with the metal center to form a stable complex that resists self-polymerization, thereby protecting the catalytic active sites while allowing the catalytic function to proceed.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If metal Schiff base complex is used for catalysis, then reaction efficiency is improved, but formation of oxo-bridged dimer occurs causing inactivation

Engineering Contradiction:

Improvereaction efficiencyVSAvoidself-polymerization leading to inactivation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the potentially harmful self-polymerization tendency into a beneficial coordinated structure. By introducing phenothiazine, the metal center's tendency to aggregate is redirected toward forming a stable, well-defined complex structure that maintains catalytic activity while preventing uncontrolled polymerization that would lead to inactivation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The phenothiazine compound is introduced in advance to preemptively protect the metal center from self-polymerization. By establishing the phenothiazine-metal coordination first, the catalyst is pre-stabilized against the harmful aggregation process before the catalytic cycle begins, preventing inactivation from occurring.

Inventive Principle:

Principle #9Preliminary anti-action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The phenothiazine metal Schiff base catalyst exhibits high activity, good selectivity, and strong stability, effectively synthesizing cyclic carbonates with minimal by-products, suitable for industrial applications.

Implementation Method 1

forms phenothiazine free radicals to protect the central metal, inhibiting self-polymerization

Methodology Applied

Scientific EffectFree radical formation:

Implementation Method 2

inhibiting self-polymerization and enhancing catalyst stability and activity

Methodology Applied

Scientific EffectSelf-polymerization inhibition:

Implementation Method 3

catalyze the reaction between carbon dioxide and an epoxide to synthesize the cyclic carbonate

Methodology Applied

Scientific EffectCatalysis: Catalysis

Data Source

PatentUS12502661B2Catalysts for synthesizing cyclic carbonates, preparation methods and uses thereof

Publication Date: 2025.12.23 ANHUI CONCH MATERIAL TECHNOLOGY CO LTD

AI summary

The present invention provides a catalyst for synthesizing a cyclic carbonate and a preparation method and use thereof. A diamine compound X, a salicylaldehyde-containing compound and a metal source M are subjected to reaction, and then added with a phenothiazine compound Y for continuous reaction to obtain a phenothiazine metal Schiff base catalyst. The formation of phenothiazine free radicals by phenothiazine compounds with a central metal can protect the central metal in the course of reaction and inhibit inactivation caused by the self-polymerization of the central meta, thus improving the activity and stability of a catalyst. Phenothiazine compounds can be present as a polymerization inhibitor to inhibit the generation of by-products such as polycarbonates and polyethylene glycol and enhance the selectivity of the catalyst during the reaction. The phenothiazine compounds are alkaline and can adsorb and activate carbon dioxide during reaction, which helps to improve the reaction efficiency. The phenothiazine metal Schiff base catalyst prepared in the present invention has high activity, strong stability and good selectivity and thus, can achieve the efficient catalyzed synthesis of cyclic carbonates under mild conditions.