Covalent organic frameworks (COFs) have emerged as promising materials for the capture and photoluminescent detection of pharmaceutical contaminants in aquatic environments due to their tunable porosity, high surface area, and structural versatility. This review summarizes recent advances in pristine COFs and COF-based hybrid materials for water treatment, focusing on both the adsorption and photoluminescent sensing of pharmaceutical pollutants. The influence of framework design, linkage type, and functionalization on adsorption performance and selectivity is discussed, together with the main interaction mechanisms involved. In addition, recent developments in photoluminescent COFs for sensitive and rapid drug detection are highlighted. Attention is given to dual-function materials capable of simultaneous capture and detection, which represent an emerging strategy for efficient water remediation. Finally, current challenges related to stability, selectivity, and real-world applicability are outlined, providing perspectives for the design of next-generation COF-based systems.

MOF@COF composites have emerged as a promising class of engineered materials with unique functionalities, combining the high porosity and tunability of metal-organic frameworks (MOFs) with the chemical and mechanical stability of covalent-organic frameworks (COFs). While their advantageous properties are well-recognized, their structural intricacies and the nature of the interfacial interactions remain insufficiently explored. In this study, an Fe-MOF@COF composite is presented, exhibiting dual functionalities for the efficient removal of organic pollutants from water. The enhanced performance is attributed to the unique properties of the MOF-COF interface, where synergistic interactions between the two porous materials play a critical role. Advanced synchrotron techniques were employed to probe interfacial interactions at the atomic and molecular levels. These findings underscore the potential of Fe-MOF@COF composites as highly effective materials for water remediation, providing deeper insights into their structural behavior and interfacial properties.

Advanced water treatment technologies must offer selective, efficient, and cost-effective contaminant removal. In this study, TPB-DMTP-COF-SH, prepared from 1,3,5-tris(4-aminophenyl)benzene (TPB) and 2,5-dimethoxyterephaldehyde (DMTP), was synthesized via a two-step method and applied for the adsorption of aluminum (Al3+), iron (Fe2+), and manganese (Mn2+) ions from water. Adsorption performance was influenced by pH, initial concentration, and contact time, with optimal pH values of 3 for Al3+, 8 for Fe2+, and 10 for Mn2+. The adsorption data followed the Langmuir isotherm model, yielding maximum capacities of 3.27 mg g-1 (Al3+), 8.5 mg g-1 (Fe2+), and 0.67 mg g-1 (Mn2+). Kinetic studies indicated a pseudo-second-order mechanism, suggesting chemisorption as the dominant process. Equilibrium adsorption was reached at 15 min for Al3+ and Mn2+ and 20 min for Fe2+. As a proof of concept, we demonstrate that this thiol-functionalized COF not only effectively removes metals but also offers enhanced processability into composite beads and membranes, making it a strong candidate for real-world water treatment applications. These findings highlight TPB-DMTP-COF-SH as a promising and scalable solution for water purification.

Post-synthetic modification (PSM) is a useful strategy to introduce new functional groups to metal-organic framework (MOF) structures in order to tune their properties for different applications.

Herein, we report the first example of MOF synthesis employing aluminum slags as a waste resource. This synthesis was exclusively carried out from waste materials, under ambient conditions in water, thus aligning with the guiding principles of Green Chemistry. The resulting MIL-53(Al) material was further functionalized with SnO2 nanoparticles and tested as catalyst for the dehydration of glucose to 5-hydroxymethylfurfural (5-HMF), showing a tenfold increase in catalytic efficiency compared to unsupported SnO2.

Metal-organic framework (MOF)-derived metal oxides blend the sensing properties of metal oxides with MOF porosity, enhancing gas sensing capabilities. In this study, M-MOFs (M = Cu, Ni and Zn) were synthesized and then calcined at different temperatures to obtain their corresponding metal oxides (CuO, NiO and ZnO). The synthesis method incorporated novel approaches to enhance sensor performance, such as optimizing calcination temperatures for improved selectivity. Structural and morphological analyses confirmed the high surface area and porosity of the metal oxide materials, facilitating efficient gas adsorption and promoting enhanced sensor response. Gas sensing studies revealed significantly enhanced performance of MOF-derived metal oxides over M-MOFs, strongly influenced by calcination temperature. Moreover, CuO, NiO and ZnO MOF-derived metal oxides showed improved selectivity towards H2S, CO and H2 gases, respectively. This study demonstrates that tuning MOF and calcination parameters can tailor sensor selectivity effectively.

Copper meets MOF-808 for water remediation: our innovative mixed-matrix membranes incorporating Cu–MOF-808 offer a sustainable solution for efficiently removing endocrine-disrupting compounds from water sources with minimal metal leaching.

The development of catalysts is crucial for sustainable chemistry, and heterogeneous catalysis, specifically, can be environmentally friendly and recyclable. Catalyst immobilization in materials has been explored, in which mesoporous silica materials have shown outstanding results in catalysis. Photocatalysis has also gained attention, providing solutions for organic synthesis and late-state functionalization, mainly using homogeneous catalysts and organic solvents. The use of aqueous media for photocatalytic reactions is particularly attractive from a sustainability perspective yet can influence reaction chemoselectivity. However, poor solubility of the organic substrates and the catalyst limits photocatalytic methods in water. Mesoporous silicas are water-stable materials suitable for catalytic applications in such media, including photocatalysis. In this work, we demonstrate an atom transfer radical addition (ATRA) reaction in water using immobilized 10-phenylphenothiazine (PTH) catalyst on different mesoporous silica supports, showing improved photocatalytic performance compared to homogeneous conditions and substrate selectivity depending on the hydrophobicity of the alkene.

Aerogels of two imine-based COFs showed fast adsorption uptakes of Fe 2+ from contaminated waters. COF-aerogel@Polysulfone composite beads are easily incorporated into water treatment, they are excellent candidates for large-scale preparation.

Metal Organic Frameworks (MOFs) present high surface areas, various pore topology as well as good stabilities. The functionalities and porosity can be tuned by using different linkers with various functional groups and a wide range of linker lengths. These properties make them good candidates in membrane separation applications. In this work, we propose a simple UiO-66 MOF-based membrane fabrication method following two steps. First, the α-alumina tubular membrane support was dip-coated with MOF-polymer hybrid nanoparticles (NPs). These NPs were prepared via one-pot synthesis by adding poly (methacrylic acid)-b-poly (methyl methacrylate) (PMAA-b-PMMA) NPs to the classical acetic acid-modulated UiO-66 or UiO-66-NH2 synthesis formulation. Second, secondary membrane growth was applied to give rise to a continuous and homogeneous crystalline MOF membrane layer. The gas permeances (He, N2, CO2 and SF6) tests confirmed high membrane permeability with no macro-defects. The as-prepared membranes that were used for dye separation (Rhodamine B) showed relatively good separation capacity.

Colloidaly stable carboxylate-based metal organic frameworks (MOFs), grown from acid decorated nanoparticles synthesized via PISA.

Porosity and surface area analysis play a prominent role in modern materials science, where 123 their determination spans the fields of natural sciences, engineering, geology and medical 124 research. At the heart of this sits the Brunauer-Emmett-Teller (BET) theory,[1] which has been 125 a remarkably successful contribution to the field of materials science. The BET method was 126 developed in the 1930s and is now the most widely used metric for the estimation of surface 127 areas of porous materials.[2] Since the BET method was first developed, there has been an 128 explosion in the field of nanoporous materials with the discovery of synthetic zeolites,[3] 129 nanostructured silicas,[4–6] metal-organic frameworks (MOFs),[7] and others. Despite its 130 widespread use, the manual calculation of BET surface areas causes a significant spread in 131 reported areas, resulting in reproducibility problems in both academia and industry. To probe 132 this, we have brought together 60 labs with strong track records in the study of nanoporous 133 materials. We provided eighteen adsorption isotherms and asked these researchers to 134 calculate the corresponding BET areas, resulting in a wide range of values for each one. We 135 show here that the reproducibility of BET area determination from identical isotherms is a 136 largely ignored issue, raising critical concerns over the reliability of reported BET areas in 137 the literature. To solve this major issue, we have developed a new computational approach 138 to accurately and systematically determine the BET area of nanoporous materials. Our 139 software, called BET Surface Identification (BETSI), expands on the well-known Rouquerol 140 criteria and makes, for the first time, an unambiguous BET area assignment possible.

UiO-MOFs are based on zirconium cluster and carboxylic acid linkers. They have excellent chemical and thermal stability, tolerance to linkers of different length and functionalities, making them good candidates for a broad range of applications. However, difficulties of processing the polycrystalline powder of MOFs limit their application. Here, we report for the first time the synthesis of the UiO-66 in the presence of a well-defined poly (methacrylic acid)-b-poly (methyl methacrylate) (PMAA-b-PMMA) nanoparticles (NPs) prepared via Reversible Addition-Fragmentation Chain-transfer Polymerization controlled Polymerization Induced Self-Assembly (RAFT-PISA). The PMAA-b-PMMA NPs with multi carboxylic acid groups on their surface, well defined in shape and size, act as multivalent connecting agent for the synthesis of the UiO-66. The resulting colloidally stable UiO-polymer NPs are crystalline, porous, and with an improved processability as was demonstrated by the preparation of a thin film nanocomposite (TFN) membrane. This membrane was applied in the filtration of Nickel (II) phthalocyanine-tetrasulfonic acid tetrasodium salt aqueous solution obtaining a water permeability circa 20 L m- 2 h-1 bar-1 with a rejection of more than 90%. This unprecedented facile synthesis approach could be universally applied to other MOFs, expanding their application in different fields due to their enhanced processability.

Global population growth and water resource scarcity are significant social problems currently being studied by many researchers focusing on finding new materials for water treatment. The aim is to obtain quality water suitable for drinking and industrial consumption. In this sense, an emergent class of crystalline porous materials known as Covalent-Organic Frameworks (COFs) offers a wide range of possibilities since their structures can be designed on demand for specific applications. Indeed, in the last decade, many efforts have been made for their use in water treatment. This perspective article aims to overview the state-of-the-art COFs collecting the most recent results in the field for water detection of pollutants and water treatment. After the introduction, where we overview the classical design strategies on COF design and synthesis for obtaining chemically stable COFs, we summarize the different experimental methodologies used for COFs processing in the form of supported and free-standing membranes and colloids. Finally, we describe the use of COFs in processes involving the detection of pollutants in water and wastewater treatment, such as the capture of organic compounds, heavy metals, and dyes, the degradation of organic pollutants, as well as in desalination processes. Finally, we provide a perspective on the field and the potential technological use of these novel materials.

Better and more efficient membranes are needed to face imminent and future scientific, technological and societal challenges. New materials endowed with enhanced properties are required for the preparation of such membranes. Metal and Covalent Organic Frameworks (MOFs and COFs) are a new class of crystalline porous materials with large surface area, tuneable pore size, structure, and functionality, making them a perfect candidate for membrane applications. In recent years an enormous number of articles have been published on the use of MOFs and COFs in preparation of membranes for various applications. This review gathers the work reported on the synthesis and preparation of membranes containing MOFs and COFs in the last 10 years. Here we give an overview on membranes and their use in separation technology, discussing the essential factors in their synthesis as well as their limitations. A full detailed summary of the preparation and characterization methods used for MOF and COF membranes is given. Finally, applications of these membranes in gas and liquid separation as well as fuel cells are discussed. This review is aimed at both experts in the field and newcomers, including students at both undergraduate and postgraduate levels, who would like to learn about preparation of membranes from crystalline porous materials.

Covalent organic frameworks (COFs) are crystalline and porous materials with bi- or three-dimensional structures built up by connecting their molecular precursors by dynamic covalent bonds. Using bottom-up or top-down strategies, bi-dimensional COFs can be obtained as single- or few-layer materials, thus enlarging the family of 2D-materials based on graphene. The main advantage of 2D-materials based on COFs is the fact that they can be chemically designed, thus allowing the formation of á la carte materials with well-designed functionalities including their size and features of their pores. The aim of this perspective review is to illustrate in a rational way the current state-of-the-art in the field of COF nanosheet formation using the two general approaches of material nano-structuring. This article reviews a selected collection of samples that illustrates the essential concepts, strategies of preparation following the two general approaches, bottom-up and top-down, and a selection of COF nanolayers showing seminal properties and potential material applications. Finally, we provide some perspectives of this novel research field.

Coordination Polymers (CPs) are periodic architectures defined by the assembly of metal entities and ligands through coordination bonds. They can be designed to present porous architectures, known as Metal-Organic Frameworks (MOFs). They can be prepared as bulk materials and at the nanoscale using bottom-up synthesis or top-down approaches. Nanoscale CPs are a subject of high current interest due to the new physicochemical properties that they can show because of confinement effects as well as their material process-ability. We present several selected CP samples with different electronic properties, electrical conductivity and/or emission, as well as ways to down-size their scale to obtain CP nanostructures. Studies on their physical properties at the nanoscale show the relevance of the confinement effects and the presence of defects, which can be controlled during the preparation process. Indeed, defect engineering is an extremely relevant tool to manipulate the material crystal quality and its specific properties. Therefore, engineered defects are gaining attention in both CPs and their porous version, MOFs, because of their implications for both physical properties and properties affecting catalysis and sorption. However, this is still a very poorly developed field. The main scope of this chapter is to provide a general overview of the impact that defects may have on the chemical, physical, electrical and/or optical properties, as well as in catalysis and sorption capabilities of some CPs, and the way to gain control of the defect production. We have selected two relevant types of 1D CP families, MMX and Cu2I2 double chains, to discuss their electronic properties and the influence that the incorporation of defects has on them. MMX chains based on the assembly of two dimetallic entities: [Pt-2(dta)(4)] (dta = ditiocarboxylate) and [Pt-2(dta)(4)I-2], behave as metallic conductors at room temperature in bulk and at the nanoscale, but the weakness of the Pt-I coordination bonds facilitates the occurrence of defects such as iodine vacancies, which significantly alter their conductivity. Their preparation at the nanoscale is feasible based on the reversible process between [Pt-2(dta)(4)] and [Pt-2(dta)(4)I-2]. Thus, the polymer [Pt-2(dta)(4)I-2](n) can be solubilized or sublimated to produce [Pt-2(dta)(4)] and [Pt-2(dta)(4)I-2] and rearrange back to [Pt-2(dta)(4)I-2](n) even on-surfaces. The exquisite control of the assembling process gives rise to a number of structural defects present along the MMX chains. In any case, electrical measurements in single chains of [Pt-2(dta)(4)I-2](n) currently postulated these CPs among the best molecular wires. We also describe several examples of Cu2I2 double chains grafted with N-aromatic terminal ligands. They show interesting electronic properties as emission and semi-conductivity. The general structural core of these 1D-CPs is based on a Cu2I2 double chain which is very sensitive to chemical and physical stimuli. We discuss the use of these CPs as stimuli-response materials, their bottom-up preparation using fast precipitation and the use of these nanostructures to prepare novel composites as multifunctional ultra-thin films. Moreover, we also show the possibility of modulating their physical properties upon the creation of structural defects. Finally, we describe different synthetic pathways (pre- and post-synthesis) to harness the incorporation of both local- and long-range defects in MOFs, resulting in altered chemistry and structures without compromising the porous scaffold. The role of defects in MOF properties related to catalysis, sorption and conductivity is widely discussed in this chapter, highlighting the importance of using advanced scanning probe microscopy, synchrotron X-rays and neutron techniques to achieve a better understanding of these functional nanomaterials.

Schiff-condensation reactions carried out between 1,6-diaminopyrene (DAP) and the tritopical 1,3,5 benzenetricarbaldehyde (BTCA) or 2,4,6-triformylphloroglucinol (TP) ligands give rise to the formation of two-dimensional imine-based covalent-organic frameworks (COFs), named IMDEA-COF-1 and -2, respectively. These materials show dramatic layer-packing-driven fluorescence in solid state arising from the three-dimensional arrangement of the pyrene units among layers. Layer stacking within these 2D-COF materials to give either eclipsed or staggered conformations can be controlled, at an atomic level through chemical design of the building blocks used in their synthesis. Theoretical calculations have been used to rationalize the different preferential packing between both COFs. IMDEA-COF-1 shows green emission with absolute photoluminescence quantum yield of 3.5% in solid state. This material represents the first example of imine-linked 2D-COF showing emission in solid state.

We present the novel potential application of imine-based covalent organic frameworks (COFs), formed by the direct Schiff reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarbaldehyde building blocks in m-cresol or acetic acid, named RT-COF-1 or RT-COF-1Ac/RT-COF-1AcB. The post-synthetic treatment of RT-COF-1 with LiCl leads to the formation of LiCl@RT-COF-1. The ionic conductivity of this series of polyimine COFs has been characterized at variable temperature and humidity, using electrochemical impedance spectroscopy. LiCl@RT-COF-1 exhibits a conductivity value of 6.45 × 10-3 S cm-1 (at 313 K and 100% relative humidity) which is among the highest values so far reported in proton conduction for COFs. The mechanism of conduction has been determined using 1H and 7Li solid-state nuclear magnetic resonance spectroscopy. Interestingly, these materials, in the presence of controlled amounts of acetic acid and under pressure, show a remarkable processability that gives rise to quasi-transparent and flexible films showing in-plane structural order as confirmed by X-ray crystallography. Finally, we prove that these films are useful for the construction of proton exchange membrane fuel cells (PEMFC) reaching values up to 12.95 mW cm-2 and 53.1 mA cm-2 for maximum power and current density at 323 K, respectively.