Preparation of Highly Porous Coordination Polymer Coatings on Macroporous Polymer Monoliths for Enhanced Enrichment of Phosphopeptides

Summary

A procedure for the preparation of porous hybrid separation media composed of a macroporous polymer monolith internally coated by a high surface area microporous coordination polymer is presented.

Abstract

We describe a protocol for the preparation of hybrid materials based on highly porous coordination polymer coatings on the internal surface of macroporous polymer monoliths. The developed approach is based on the preparation of a macroporous polymer containing carboxylic acid functional groups and the subsequent step-by-step solution-based controlled growth of a layer of a porous coordination polymer on the surface of the pores of the polymer monolith. The prepared metal-organic polymer hybrid has a high specific micropore surface area. The amount of iron(III) sites is enhanced through metal-organic coordination on the surface of the pores of the functional polymer support. The increase of metal sites is related to the number of iterations of the coating process.

The developed preparation scheme is easily adapted to a capillary column format. The functional porous polymer is prepared as a self-contained single-block porous monolith within the capillary, yielding a flow-through separation device with excellent flow permeability and modest back-pressure. The metal-organic polymer hybrid column showed excellent performance for the enrichment of phosphopeptides from digested proteins and their subsequent detection using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The presented experimental protocol is highly versatile, and can be easily implemented to different organic polymer supports and coatings with a plethora of porous coordination polymers and metal-organic frameworks for multiple purification and/or separation applications.

Introduction

Porous coordination polymers (PCPs) are coordination compounds based on metal centers linked by organic ligands with repeating coordination entities extending in 1, 2 or 3 dimensions that can be amorphous or crystalline^1-3. In recent years, this class of porous materials has attracted widespread attention due to their high porosity, wide chemical tunability, and their stability. PCPs have been explored for a range of applications including gas storage, gas separation, and catalysis^3-6, and very recently, the first analytical applications of PCPs have been described⁷.

Because of their enhanced chemical functi....

Protocol

NOTE: Before beginning, check all relevant material data sheets (MSDSs). Several of the chemicals used in the synthetic and application procedures are toxic. Please follow all appropriate safety practices and use adequate protective equipment (lab coat, full-length pants, closed-toe shoes, safety glasses, gloves). Please use all cryogenic personal protective equipment when handling liquid nitrogen for the nitrogen adsorption measurements (insulated gloves, face shield).

1. Porous Polymer Monolith Preparation in Bulk and Capillary Column Format

1. Bulk Polymer Monolith for Characterization
   1. Purify styrene, divinylbenzene ....

Results

A schematic illustration of the PCP growth on the pore surface of the organic polymer monolith is shown in Figure 1. In this figure, we illustrate the initial Fe(III) atoms retained on the pore surface of the original polymer monolith coordinated to carboxylic functional groups. Using the protocol described herein additional organic ligand and Fe(III) ions are added to the surface, shaping a porous coordination network within the polymer monolith. Figure 1 also shows schematically the us.......

Discussion

The original polymer monolith contains carboxylic functional groups able to bind to metals. Coordinating the initial metal sites on the original material, we are able to grow a PCP coating (Figure 1A), incorporating a number of additional metal sites shaping a microporous network. This makes the presented MOPH materials attractive for extraction or purification procedures where metallic species are involved, such as the immobilized metal-ion affinity chromatography (IMAC) technique. The general procedure.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Polyimide-coated capillaries	Polymicro Technologies	TSP100375	100 μm i.d.
3-(trimethoxysilyl)propyl methacrylate, 98%	Sigma-Aldrich	440159
Styrene, 99%	Sigma-Aldrich	W323306	Technical grade
Divinylbenzene, 80%	Sigma-Aldrich	414565
Methacrylic acid, 98%	Mallinckrodt	MK150659
Toluene, ≥99.5%	EMD chemicals	MTX0735-6
Isooctane, ≥99.5%	Sigma-Aldrich	650439
2,2'-azobisisobutyronitrile, 98%	Sigma-Aldrich	441090
Aluminium oxide (basic alumina)	Sigma-Aldrich	199443
Iron (III) chloride hexahydrate, 97%	Sigma-Aldrich	236489
1,3,5-benzenetrycarboxylic acid, 95%	Sigma-Aldrich	482749
Acetonitrile, ≥99.5%	Sigma-Aldrich	360457
Ammonium bicarbonate, ≥99.5%	Sigma-Aldrich	9830
Trifluoroacetic acid, ≥99%	Sigma-Aldrich	302031
Ethanol, ≥99.8%	Sigma-Aldrich	2854
Iodoacetamide, ≥99%	Sigma-Aldrich	I1149
Dithiothreitol, ≥99%	Sigma-Aldrich	43819
Monobasic sodium phosphate dihydrate, ≥99%	Sigma-Aldrich	71505
Dibasic sodium phosphate dihydrate, ≥99%	Sigma-Aldrich	71643
Phosphoric acid, ≥85%	Sigma-Aldrich	438081
2,5-dihydroxybenzoic acid, ≥99%	Sigma-Aldrich	85707
Trypsin	Sigma-Aldrich	T8003	Bovine pancreas
β-casein	Sigma-Aldrich	C6905	Bovine milk
ZipTip pipette tips	Merck Millipore	ZTC18S096	C18 resin