Chapter Four · failure evidence
What Porous Materials & MOFs got wrong, from 40 dissertations
The compiled records demonstrate various operational and synthetic failure points across porous materials and metal-organic frameworks. Performance limitations frequently arise from structural collapse under moisture or acidic gas exposure, pore obstruction from chemical functionalization, and competition against simpler commercial benchmark adsorbents. These records come from PhD theses at 19 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Novel porous adsorbents perform worse than commercial or simpler baseline materials
Synthesized porous materials, biochars, and metal-organic frameworks achieved lower adsorption capacities for gases, heavy metals, and organic contaminants than commercial activated carbons and zeolites. These custom adsorbents also exhibited slower conversion rates and reduced pollutant removal efficiencies compared to established benchmark materials.
Lost to a baseline
Mesoporous carbon spheres synthesized by Chen et al. (2021) achieved 3.22 mmol/g CO2 capture capacity at 75 °C and 0.05 bar, outperforming MC2-800-1-60 (2.95 mmol/g at 0.15 bar).
Development of Three-Dimensional Mesoporous Biocarbon Materials for Energy-Related Applications · University of Nottingham Repository
Lost to a baseline
Carboxylic CNT/CoFe2O4 composite achieved 250 mg/g SMX adsorption capacity, outperforming this work.
ADSORPTION OF PHARMACEUTICALS FROM CONTAMINATED WATER BY ADSORBENTS DEVELOPED FROM REED CANARY GRASS · HARVEST
Lost to a baseline
PEI-modified mesoporous carbon spheres (MCSs) by Wang et al. (2016) achieved 3.71 mmol/g CO2 capture capacity at 75 °C and 15% CO2, higher than MC2-800-1-60 (2.95 mmol/g).
Development of Three-Dimensional Mesoporous Biocarbon Materials for Energy-Related Applications · University of Nottingham Repository
Lost to a baseline
Activated carbon prepared from coal baseline achieved a higher maximum SMX adsorption capacity (264.4 mg/g) than this work's renewable adsorbent (147.9–161.3 mg/g).
ADSORPTION OF PHARMACEUTICALS FROM CONTAMINATED WATER BY ADSORBENTS DEVELOPED FROM REED CANARY GRASS · HARVEST
Lost to a baseline
Commercial activated carbon (AC) achieved 94% PFOA adsorption efficiency, outperforming PBC (92%) and ZnBC (84%) under identical batch conditions (200 µg/L PFOA, 10 h, 25 °C)
Lost to a baseline
F300 commercial activated carbon achieved higher maximum Langmuir PFOS adsorption capacity (55.7 mg/g) than SCGKOH biochar (43.4 mg/g)
Lost to a baseline
Zn-EDTA MOF CO2 adsorption capacity (164.58 ml/g) was beaten by Mg-MOF-74 (593.0 ml/g)
تحضير جسيمات أكسيد الزنك النانونية وهياكل عضوية معدنية لتقليل الانبعاثات الكربونية ومعالجة المياه · DSpace at University of El Oued
Lost to a baseline
Activated carbon (20,200 µg/g) and activated alumina (15,900 µg/g) exhibited far higher As(V) adsorption capacities than IOCB (836.4 µg/g).
Removal of arsenic from drinking water by fungal biomass and biological filtration. · oURspace
Lost to a baseline
Polyurethane sponge-supported graphene oxide-titanium phosphate achieved 228.1 mg/g and phosphorus-functionalized nanoporous carbon achieved 347.0 mg/g Dy3+ adsorption capacity, beating PCs/MB (34.0 mg/g).
Development of a novel and green Mannich reaction-modified chitosan hydrogel for dysprosium(III) recovery · Iowa State
Lost to a baseline
Fe3O4-FITC-resin MB adsorption capacity (150 mg g-1) was lower than covalent organic frameworks (~300 mg g-1), reduced graphene oxide (~200 mg g-1), and metal-organic frameworks (~180 mg g-1).
Scalable Synthesis of Nanomaterials in Continuous-Flow Reactors · Georgia Tech
Lost to a baseline
At 250 °C for 1 h with 1 wt.% ethanol, impregnated 2 wt.% Ru/CeO2 showed ~20% lower H2 productivity than commercial 5 wt.% Ru/Al2O3 (443 vs. 554 mmol H2/gRu) and lower ethanol conversion (1.3 vs. 1.7 mol/gRu) primarily due to ~21% lower surface area and microporous structure.
Valorisation of biomass-derived wastewaters via aqueous phase reforming for energy recovery: a multi-level performance assessment · IRIS - POLITO - prod
Chemical functionalization and post-synthetic modifications reduce pore volume and adsorption uptake
Functionalizing organic linkers or carbon surfaces with amines, metal ions, or counterions often reduced available pore volume and blocked gas diffusion channels. Consequently, modified sorbents showed lower gas adsorption capacities and poorer cyclic stability than unmodified framework baselines.
Tried and failed
Post-synthetic metalation of functionalised porous frameworks applied to gas adsorption selectivity. Outcome: worse than baseline. Reason: Metal coordination reduced available adsorption sites and pore volume compared to unmetalated framework
Metal-Organic Framework Structure-Property Relationships for Selective Sulfur Dioxide Adsorption · Georgia Tech
Tried and failed
post-synthetic amine functionalization for cyclic gas adsorption applied to metal-organic frameworks in dynamic breakthrough. Outcome: unstable. Reason: significant loss of adsorption capacity over repeated adsorption-desorption cycling compared to carbon and zeolites
Influence Of Water Vapor on the Adsorption of Exhaled Breath-Borne VOC Biomarkers for COVID-19 · Georgia Tech
Tried and failed
amine functionalization for low-concentration gas capture applied to porous materials for direct air capture. Outcome: worse than baseline. Reason: most amine-functionalized candidates failed performance screening criteria despite standard expectations for carbon dioxide capture
Accurate Predictions of the Adsorption Space and Efficient Sorbent Discovery in Metal-Organic Frameworks · Georgia Tech
Lost to a baseline
Non-functionalized activated carbon outperformed G2CO3-impregnated AC (10p, 15p, 20p) in pure CO2 adsorption at pressures above 45 kPa (5.044 mmol/g for AC vs 3.699-4.607 mmol/g).
Evaluating the Effect of Composition, Structure and Functionality on Atmospheric CO2 Adsorption in Porous Solid Sorbents · Virginia Tech
Lost to a baseline
Neat MIL-101-Cr-4 and MIL-101-Cr-10 outperformed their EN-functionalized counterparts in pure CO2 adsorption (7.09 vs 6.1 mmol/g and 7.35 vs 1.65 mmol/g).
Evaluating the Effect of Composition, Structure and Functionality on Atmospheric CO2 Adsorption in Porous Solid Sorbents · Virginia Tech
Tried and failed
gas-phase halogenation of porous framework linkers applied to small-pore metal-organic frameworks. Reason: small pore apertures restricted mass transport, causing pore blockage, incomplete reaction, and framework degradation
Tried and failed
amine functionalization of organic linkers applied to low-pressure hydrogen adsorption in metal-organic frameworks. Outcome: worse than baseline. Reason: functional groups reduced pore volume and surface area without introducing sufficiently strong binding sites for hydrogen
Mixture Adsorption in Metal-Organic Frameworks for Biogas and Light Hydrocarbon Separation · Georgia Tech
Tried and failed
room-temperature synthesis of ionic metal-organic frameworks applied to porous materials for gas adsorption. Reason: extraframework counterions completely obstructed internal pore channels and structural voids to gas molecules
Tried and failed
incorporating hydrophilic functional groups into porous frameworks applied to metal-organic framework water sorption. Outcome: worse than baseline. Reason: more hydrophilic substituents failed to lower the condensation relative humidity threshold compared to larger halides
Sorption-based atmospheric water harvesting: from atoms to applications · MIT
Exposure to water and humid cycling triggers hydrolytic degradation and framework collapse
Metal-organic frameworks and porous coordination frameworks suffered irreversible structural collapse and loss of surface area during repeated water adsorption cycles or steam exposure. Extended ambient humidity exposure also degraded porosity and severely reduced carbon dioxide uptake in direct air capture applications.
Tried and failed
post-synthetic hydroxide exchange applied to metal-organic frameworks for water sorption. Outcome: unstable. Reason: framework lost structural stability upon repeated water adsorption and desorption cycles
Tailoring Metal–Organic Frameworks for Water Harvesting · MIT
Tried and failed
rapid thermal dehydration in humid atmosphere applied to metal-organic frameworks for adsorption. Outcome: unstable. Reason: framework collapsed forming metal oxide domains within minutes instead of generating coordinatively unsaturated sites
Tried and failed
solvothermal synthesis using dimethylformamide solvent applied to porous coordination frameworks. Outcome: unstable. Reason: residual solvent or defective coordination caused rapid hydrolytic degradation and structural collapse during water cycling
Tailoring Metal–Organic Frameworks for Water Harvesting · MIT
Tried and failed
water vapor adsorption beyond isotherm threshold applied to microporous coordination framework adsorbent. Outcome: unstable. Reason: moisture exposure caused irreversible structural collapse, severely reducing surface area and pore volume
Tried and failed
zinc-based metal-organic frameworks for cyclic adsorption applied to atmospheric water harvesting. Outcome: unstable. Reason: poor hydrolytic stability causing rapid loss of sorption capacity and surface area upon water cycling
Tailoring Metal–Organic Frameworks for Water Harvesting · MIT
Tried and failed
direct air capture using fluorinated MOFs applied to low-concentration CO2 adsorption in humid air. Outcome: unstable. Reason: extended exposure to humidity and ambient conditions causes severe loss of porosity and CO2 uptake capacity
Considered and rejected
Considered and rejected: rejected hydrotalcites and base metal oxides as water sorbents due to loss of steam adsorption capacity at methanol synthesis operating temperatures
High mass loading and intraparticle mass transfer resistances degrade porous electrode performance
Excessive electrodeposition loading on porous carbon electrodes increased electrical resistance and triggered active material dissolution during cycling. In addition, intraparticle mass transport limitations and mechanical deformation compromised catalyst selectivity and electrode stability.
Tried and failed
carbon nanotube immobilised molecular catalysts without stirring applied to photochemical carbon dioxide reduction. Outcome: worse than baseline. Reason: mass transport limitations in porous nanotube sheets under high flux reduced product selectivity
Organic Semiconductor-BiVO4 Tandem Devices for Solar-Driven H2O and CO2 Splitting. · Cambridge
Lost to a baseline
Cu-Mg-Al MMO-11 exhibited slower oxygen release and re-oxidation rates than the more porous Cu-Mg-Al MMO-9.5 due to higher intraparticle mass transfer resistances
Layered double hydroxide-derived oxygen carriers for chemical looping processes · Imperial
Tried and failed
prolonged electrodeposition of metal oxide applied to porous carbon supercapacitor electrodes. Outcome: worse than baseline. Reason: excessive active material loading increased electrical resistance, reducing specific capacitance at high scan rates
Electrochemical studies of the applications of novel carbon-based materials · Oxford
Tried and failed
block copolymer electrospun porous carbon fibers applied to flexible supercapacitor electrodes. Outcome: unstable. Reason: severe mechanical deformation caused structural degradation and contact loss in gel electrolyte
Block Copolymer Derived Porous Carbon Fiber for Energy and Environmental Science · Virginia Tech
Tried and failed
high mass loading of electrodeposited metal oxide applied to porous carbon supercapacitor electrodes. Outcome: unstable. Reason: active material dissolution and structural degradation during cycling
Electrochemical studies of the applications of novel carbon-based materials · Oxford
Lost to a baseline
Low-frequency capacitance of LIG potassium ISEs (~48-51 µF in water) was substantially lower than colloid-imprinted mesoporous (CIM) carbon contacts and carbon black nanocomposites (<1 µV/h drift).
Exposure to acidic gases or thermal activation causes framework degradation and collapse
Acidic gases like sulfur dioxide and hydrogen sulfide attacked coordination frameworks, causing metal sulfide formation, loss of crystallinity, and structural failure. In addition, heating during degassing activation caused flexible or weakened frameworks to buckle and lose their internal pore volume.
Tried and failed
gas capture using metal-organic frameworks applied to hydrogen sulfide adsorption. Outcome: unstable. Reason: framework degradation and loss of porosity occurred due to metal sulfide formation
Tried and failed
thermal activation degassing applied to metal-organic framework gas sorption. Outcome: unstable. Reason: the porous framework collapsed upon heating during the degassing process
Silicon-based hexacarboxylic acids and their application in metal-organic frameworks · Imperial
Tried and failed
post-synthetic metal coordination of functionalized porous frameworks applied to acidic gas adsorption. Outcome: unstable. Reason: Metal coordination weakened framework stability, leading to structural collapse upon sulfur dioxide exposure.
Metal-Organic Framework Structure-Property Relationships for Selective Sulfur Dioxide Adsorption · Georgia Tech
Tried and failed
ligand functionalization with nitrogen heterocycles applied to metal-organic framework gas adsorption. Outcome: unstable. Reason: exposure to acidic gas caused framework collapse, severe loss of crystallinity, and porosity degradation
Tuning metal-organic frameworks for flue gas desulfurization · Georgia Tech
Tried and failed
incorporating flexible heterocyclic linkers in metal-organic frameworks applied to porous coordination framework synthesis. Outcome: unstable. Reason: framework collapsed and buckled upon activation due to excessive ligand flexibility, resulting in loss of porosity
Development of metal-organic frameworks based on N-heterocyclic ligands · EPFL
Harsh synthetic conditions and metalation cause undesired phases and metal nanoparticle aggregation
Elevated temperatures and altered synthesis parameters induced precursor reduction, nanoparticle aggregation, or the formation of unintended crystalline phases with low adsorption capacity. Mechanical processing like ball-milling and post-synthetic metal coordination also degraded crystal structures and caused unintended metal exchange at structural nodes.
Tried and failed
Post-synthetic metalation of Lewis-basic porous frameworks applied to phosphine-functionalized metal-organic frameworks. Outcome: unstable. Reason: Crystal degradation, desolvation, and unintended metal exchange at structural nodes prevented structural characterization.
Tried and failed
increasing base concentration and antisolvent ratio in synthesis applied to continuous flow metal-organic framework synthesis. Reason: favored formation of an undesired crystalline phase with poor gas adsorption capacity
Magnetic framework composites for CO2 capture · University of Nottingham Repository
Tried and failed
ball-milling precursor mixture for porous film fabrication applied to fuel cell cathode catalyst layers. Outcome: worse than baseline. Reason: loss of macroporous structure during processing led to significantly reduced mass activity
Engineering the cathode catalyst layer architecture for fuel cells · Imperial
Tried and failed
High-temperature direct metallation of porous frameworks applied to metal-organic framework single-site metal loading. Outcome: unstable. Reason: Excess thermal energy caused precursor reduction and unwanted metal nanoparticle aggregation instead of single-site coordination
Considered and rejected
Considered and rejected: Rejected hard-template mesoporous synthesis due to low yields and requirement of hazardous etching reagents (NaOH, HF).
Scalable Synthesis of Nanomaterials in Continuous-Flow Reactors · Georgia Tech
Surface modifications on mesoporous nanoparticles cause burst release and erratic delivery kinetics
Polymer coatings on mesoporous nanoparticles triggered particle agglomeration and rapid burst release of cargo instead of controlled release. In vitro release measurements also failed to predict rapid in vivo clearance, while certain mesoporous oxide templates showed non-selective toxicity to healthy cells.
Tried and failed
polysaccharide surface coating for controlled release applied to mesoporous inorganic nanoparticles. Outcome: unstable. Reason: coating induced nanoparticle agglomeration and triggered non-selective burst release of loaded ions
Inorganic nanoparticles for cancer therapy · Imperial
Tried and failed
surface modification for sustained drug release applied to mesoporous biomaterial vaccine delivery systems. Outcome: did not generalise. Reason: in vitro release kinetics failed to predict in vivo rapid clearance indistinguishable from unmodified controls
Developing strategies to enhance immune responses induced by mesoporous silica rod vaccines · Harvard
Considered and rejected
Considered and rejected: Rejected GeO2 and GeO2-ZnO-SiO2 mesoporous nanoparticle templates due to poor dissolution, lack of selective cancer cytotoxicity, and unwanted toxicity to normal breast cells.
Inorganic nanoparticles for cancer therapy · Imperial
Left open by the authors
Problems the authors named and did not get to.
Left open
Test higher activation temperatures on N-doped mesoporous carbons to restore CO2 adsorption capacity after moist flue gas exposure. Blocker: Requires a materials synthesis and gas adsorption wet lab to treat materials and measure adsorption capacities.
Versatile, direct nanocasting strategy to N-rich ordered mesoporous carbons for selective post-combustion CO2 capture and energy storage · IRIS - POLITO - prod
Left open
Determine optimal desorption methods and measure the cycle life limits for VOC-loaded functionalized MOF and activated carbon adsorbent capsules. Blocker: Requires physical synthesis of MOFs, adsorption capsules, dynamic breakthrough gas chromatography apparatus, and wet lab facilities
Influence Of Water Vapor on the Adsorption of Exhaled Breath-Borne VOC Biomarkers for COVID-19 · Georgia Tech
Left open
Optimize the layering of functionalized MOF and activated carbon adsorbent beds for multicomponent dynamic breakthrough adsorption of breath-borne VOCs. Blocker: Requires experimental synthesis of functionalized MOFs and dynamic breakthrough gas chromatography testing apparatus under humid conditions.
Influence Of Water Vapor on the Adsorption of Exhaled Breath-Borne VOC Biomarkers for COVID-19 · Georgia Tech
Left open
Modify Zn-EDTA MOF structure and increase adsorbent dosage to evaluate and optimize CO2 capture efficiency and saturation limits. Blocker: Requires wet lab chemical synthesis and physical gas adsorption testing apparatus
تحضير جسيمات أكسيد الزنك النانونية وهياكل عضوية معدنية لتقليل الانبعاثات الكربونية ومعالجة المياه · DSpace at University of El Oued
Left open
Screen alternative MOF materials using the CO2 mass transfer and adsorption model to identify candidates with higher capacity or lower cost. Blocker: None
CARBON DIOXIDE ADSORPTION ON MOFS-COATED WIND TURBINE BLADES: MODELING AND FACTORS INFLUENCING ADSORPTION RATE · JScholarship
Left open
Synthesize and evaluate activated carbon-supported controls with various anions and guanidinium-carboxylic acid networks for CO2 adsorption. Blocker: Requires chemical synthesis lab and experimental breakthrough column testing apparatus.
Evaluating the Effect of Composition, Structure and Functionality on Atmospheric CO2 Adsorption in Porous Solid Sorbents · Virginia Tech
Left open
Evaluate dynamic breakthrough adsorption behavior of low-concentration (<= 10 ppm) VOC biomarkers on functionalized MOFs and activated carbons. Blocker: Requires wet lab synthesis of functionalized MOFs and dynamic breakthrough gas chromatography testing apparatus.
Influence Of Water Vapor on the Adsorption of Exhaled Breath-Borne VOC Biomarkers for COVID-19 · Georgia Tech
Left open
Measure dynamic CO2 adsorption capacity on MIL-101(Cr) before and after saturation exposure to SO2/NO2 across various partial pressures. Blocker: Requires a wet chemistry laboratory, physical MOF synthesis/activation, and gas breakthrough measurement apparatus.
Stability and Adsorption Properties of Metal-Organic Frameworks for Acid Gases · Georgia Tech
Left open
Synthesize and mechanistically characterize mesoporous MgO sorbents promoted with different or mixed alkali metals (Li, Na, K, Rb) for CO2 capture. Blocker: Requires a wet chemistry laboratory, chemical precursors, and physical characterization instruments.
Investigation Of Catalytic Sorbents For Capture And Conversion Of CO2 To Methane · Georgia Tech
Left open
Conduct comprehensive field testing of activated carbon adsorption capacities for multiple pollutants and heavy metals beyond arsenic. Blocker: Requires physical synthesis of activated carbon material and wet-lab or field-testing water filtration setups.
Approaches to maximise the utilisation of residues from thermal conversion of oil palm waste. · Cranfield
Checking a claim in this area?
We can run the same search on any method or claim. If nothing turns up, we will say so, and that proves nothing on its own.