Porous Solids Research Articles

On the structural stability for a model of mixture of porous solids

The present paper is dedicated to the structural stability of the linear model of a mixture of two porous solids. It is shown that the variation of the characteristic coefficients that describe the coupling of the various mechanical effects involved in the model in concern does not destroy its structure. This means that any small variation of these coefficients leads to small variations in the corresponding solutions of the associated initial boundary value problems. For this purpose, more mathematical estimates are presented describing precisely the continuous dependence of the solutions with respect to all external given data of the initial boundary value problem, as well as with respect to appropriate measures of the set of coupling parameters. This allows the conclusion that the model of the mixture of porous materials is consistent. In particular, it is believed that the estimates obtained in terms of structural stability are particularly meaningful with regard to the materials used in building contexts and the related decay phenomena.

Production of renewable mesitylene as jet-fuel additive: Reaction kinetics of acetone self-condensation over basic (TiO2) and acid (Al-MCM-41) catalysts

Sustainable production of jet fuel additives plays an essential role to decrease greenhouse gas emissions in the aviation industry. Acetone obtained from biomass fermentation is one of the platform molecules of the bio-refinery that can be used as raw material of newly developed sustainable processes. Mesitylene jet fuel additive can be obtained by acetone self-condensation reaction catalyzed by porous solids. In the present work, TiO2 and Al-MCM-41 have been chosen, respectively, as basic and acid catalysts, because of having some tolerance to deactivation. The reaction was studied in a continuous fixed-bed reactor operated in the gas phase at space velocities of 7900 mol/kg h for TiO2 and 5000 mol/kg h for Al-MCM-41. The influence of feed concentration (5–20% acetone and 0–5% mesityl oxide) and temperature (200–350 °C) was studied. First, the reaction scheme was assessed based on the product distribution. It was found that the acid catalyst Al-MCM-41 favors mesityl oxide decomposition to undesired isobutylene and acetic acid. Then, a mechanistic kinetic model of the different steps of the reaction scheme was developed and fitted the experimental results of each catalyst. This model constitutes a valuable tool for the scale-up of this process.

A Versatile Shaping Method of Very-High Loading Porous Solids Paper Adsorbent Composites.

Owing to their high porosity and tunability, porous solids such as metal-organic frameworks (MOFs), zeolites, or activated carbons (ACs) are of great interest in the fields of air purification, gas separation, and catalysis, among others. Nonetheless, these materials are usually synthetized as powders and need to be shaped in a more practical way that does not modify their intrinsic property (i.e., porosity). Elaborating porous, freestanding and flexible sheets is a relevant shaping strategy. However, when high loadings (>70wt.%) are achieved the mechanical properties are challenged. A new straightforward and green method involving the combination softwood bleached kraft pulp fibers (S) and nano-fibrillated cellulose (NFC) is reported, where S provides flexibility while NFC acts as a micro-structuring and mechanical reinforcement agent to form high loadings porous solids paper sheets (>70wt.%). The composite has unobstructed porosity and good mechanical strength. The sheets prepared with various fillers (MOFs, ACs, and zeolites) can be rolled, handled, and adapted to different uses, such as air purification. As an example of potential application, a MOF paper composite has been considered for the capture of polar volatile organic compounds exhibiting better performance than beads and granules.

Decaniobate: The Fruit Fly of Niobium Polyoxometalate Chemistry.

ConspectusPolyoxometalates (POMs, metals = V4/5+, Nb5+, Ta5+, Mo5/6+, and W5/6+) can be described as molecular metal oxides. The V, Mo, and W-POMs (classic POMs) exhibit rich structural diversity with interesting redox properties, acid catalysis, inorganic ligands, and colorimetric properties and behavior. Nb and Ta POMs, while structurally similar, are generally stable only in base and redox behavior is rare, and they are synthetically far less accessible. The V, Mo, and W-POMs have been studied for well over a century, Nb-POM chemistry has emerged in the last 20 years, and Ta-POM chemistry is yet to see consistent and significant advances. Early and current success in Nb-POM chemistry is owed mainly to hydrothermal synthesis, which is wholly unsatisfying, given the black box nature of this technique.For the last 5 years and as summarized in this Account, we have exploited decaniobate, [Nb10O28]6- (Nb10), as a foundation to perform room-temperature, nearly pH-neutral manipulations of Nb-POM solutions. Nb10, with a rare neutral self-buffering pH, responds to any interactions with electrolytes (specifically oxoanions and metal cations) by undergoing transformations, leading to new topologies. The ease of Nb10 transformation yielding new generations of Nb-POMs, akin to an inorganic analogue of biological model organisms such as the fruit fly, inspired the title of this Account. The common building unit born from the disassembly of Nb10 is [Nb7O20(OH, H2O)2](5-7)-, and the hydroxyl/aqua ligands provide reactivity for linking via condensation reactions, ligand exchange, heterometals, or oxoanions. We can coax these newly assembled Nb-POMs (detected by small-angle X-ray scattering, SAXS) to crystallize via the usual methods of vapor diffusion, salting out, and reduced temperature, and the single-crystal X-ray diffraction structures are valuable for understanding reaction mechanisms to fine-tune control and yield a landscape of topologies and compositions. Beyond providing an opportunity to comprehend and diversify POM chemistry, the reactivity of Nb10 yields highly soluble (i.e., >2 M Nb), nearly neutral aqueous solutions of niobium, ideal for the solution-phase deposition of thin films, demonstrated with LiNbO3, (Na,K)NbO3, Nb2O5, and heterometal-doped Nb2O5. The obtained films are cohesive and smooth, enabled by the tendency of these solutions to gel if simply evaporated quickly.Per our current endeavors, this gelation behavior provides an opportunity to develop new soft, flexible materials including inorganic networks, organic-inorganic networks, and porous solids and explore their material properties including base catalysis and sorption (i.e., CO2). Nb-POM (and Ta-POM) discovery and implementation of properties is far from complete. While heterometal (d and f element) substitution is easy with classic POMs, imparting a whole host of functions (tuned luminescence, catalysis, electroactivity, etc.), it remains a challenge with Nb-POMs due to pH incompatibility with most heterometals. This grand challenge that defies fundamental aqueous behavior of metal cations requires the creation of liquid mixtures that include polymer and/or ionic liquid components, and the creation of such reaction media can impact synthesis beyond POM chemistry. The goal of this Account is to describe the recent advances in Nb-POM chemistry, afforded by the Nb10 "fruit fly", and to also provide insight into the next large steps needed to advance Nb-POM chemistry.

Insight into the Isoreticularity of Li-MOFs for the Design of Low-Density Solid and Quasi-Solid Electrolytes.

Isoreticularity in metal organic frameworks (MOFs) allows the design of the framework structure and tailoring the pore aperture at the molecular level. The optimal pore volume, long-range order of framework expansion, and crystallite size (grain size) could enable improving Li-ion conduction, thereby providing a unique opportunity to design high-performance solid and quasi-solid electrolytes. However, definitive understanding of the pore aperture, framework expansion, and crystallite size on the Li-ion conduction and its mechanism in MOFs remains at the exploratory stage. Among the different MOF subfamilies, Li-MOFs created by the isoreticular framework expansion using dicarboxylates of benzene, naphthalene, and biphenyl building blocks emerge as low-density porous solids with exceptional thermal stability to study the solid-state Li+ transport mechanisms. Herein, we report the subtle effect of the isoreticularity in Li-MOFs on the performance of solid and quasi-solid-state Li+ conduction, providing new insight into Li+ transport mechanisms in MOFs for the first time. Our experimental and computational results show that the reticular design on an isostructural extended framework structure with the optimal pore aperture and crystallite size can influence the Li+ conductivity, exhibiting comparable ionic conductivities to solid polymer electrolytes at room temperature. Aligning with the computational studies, our experimental absorption spectral traces of solid electrolytes prepared by encapsulating lithium salt (LiClO4) and the plasticizer (ethylene carbonate) with Li-MOFs confirm the participation of the free and bound states of Li+ in a pore filling-driven ion conduction mechanism. We postulate that porous channels of Li-MOFs aid free Li+ to move through the pores via a vehicle-type mechanism, in which the pore-filled plasticizer acts as a carrier for mobile Li+ while the framework's functional sites transport the bound state of Li+ via an ion hopping mechanism from one crystallite site to another. Our computational studies performed on the Li+ conduction pathway validated the postulated pore filling mechanism and confirmed the involvement of bridging complexes, formed by binding Li+ onto the framework's functional sites as well as to the pore-filled ethylene carbonates. The Li+ diffusion energy barrier profiles along with the respective conformational changes during the diffusion of Li+ in solid electrolytes prepared from Li-BDC MOF and Li-NDC MOF strongly support the cooperative movement of Li+ ions via ion hopping along the framework's edges and vehicle-type transfer, involving the pore-filled plasticizer. Our findings suggest that cooperative function of the optimal pore volume, framework expansion, and crystallite size play a unique role in Li-ion conduction, thereby providing design guidelines for the low-density solid and quasi-solid electrolytes.

Encapsulation of thymol and limonene in metal–organic frameworks for inhibition of Colletotrichum musae growth

SummaryMonoterpenes are the most prevalent compounds found in essential oils. They exhibit inhibitory actions against phytopathogenic postharvest fungi. Direct application limits their effectiveness due to their instability, high volatility, hydrophobicity and susceptibility to degradation. Encapsulation systems using metal–organic frameworks (MOFs) have been developed to maximise their use. In this study, four protocols were shown to encapsulate thymol and limonene in porous solids, such as ZIF‐8, UiO‐66‐(COOH)2 and zeolite 13X. Vapourisation and diffusion at 60 °C for 16 h was found to be the most efficient encapsulation process. A larger amount of thymol than limonene was loaded in the porous solids. Thymol released from MOFs slowed down the growth of Colletotrichum musae by up to 6 days at 25 °C. There was a sustained release of thymol even beyond the period of maximum fungal growth. This proof‐of‐concept study revealed the potential utility of MOFs as carriers of thymol against postharvest fungi.

Swift fabrication of thin-film composite membranes with azine-linked covalent organic framework for high-temperature organic solvent nanofiltration

Covalent organic frameworks (COFs) belong to a class of crystalline and porous solids that are generated by the self-assembly of reactive monomers via covalent linkage. Most existing methods for fabricating COF membranes are tedious, and they focus on quality control challenges associated with thickness uniformity, pore size, and mechanical properties. In this study, TraHz and TpaHz COF-based thin-film composite (TFC) membranes were prepared via the swift interfacial polymerization (IP) of hydrazine and aldehyde monomers on a polyacrylonitrile (PAN) support. Hydrazine played a dual role in one-pot synthesis, where PAN was crosslinked and IP was initiated. Varying the polymerization time allowed for fine-tuning the membrane thickness and performance. The membranes displayed robust high-temperature separation performance in polar aprotic solvents at temperatures of up to 80 °C. The toluene permeance of the membranes was remarkable. The permeance was highly dependent on both the applied pressure and temperature; however, the rejection performance was less dependent on these parameters. Based on the results of the nanofiltration performance evaluated using different molecular-weight dyes, a molecular-weight cut-off value of ∼650 g mol−1 and a rejection higher than 98 % for the Congo red and Chicago blue dyes in water, THF, and ethanol were observed. The dye rejection in toluene was higher than 98 % for Rhodanile blue, while maintaining high toluene permeances of 47 and 33 L m−2 h−1 bar−1 using TraHz-30 and TpaHz-30, respectively. In addition, both membranes exhibited stable separation performance. Our TFC membranes demonstrate a new approach for designing robust and high-flux nanofiltration membranes for precise molecular sieving even at high temperatures.

A note on the response of elastic bodies whose material moduli depend on the density and the mechanical pressure

In this note we study the response of an inhomogeneous body, whose material moduli depend on the density and the mechanical pressure, that is described by an implicit constitutive relation between the Cauchy stress and the right Cauchy–Green tensor. Such a constitutive relation is relevant to the study of the deformation of porous elastic solids as the porous structure varies and the local density changes. The boundary value problems of a plate of such a material subject to uniaxial and bi-axial extension and compression are considered. We find that regions that are more porous, and thus of lower macroscopic density, have the propensity to fail than regions of higher density, in the sense the load carrying capacity decreases, when other measures such as the stress are comparable.

High pressure photoluminescence and Raman investigations of Rhodamine B absorbed on MIL 53(Fe)

Encapsulating organic dyes within porous solids is an efficient way to design luminescent composite materials and devices. However, for practice applications, the luminescence tuning and the stability investigation of such materials is still a challenge work. Here, a comparative in situ Raman spectra and photoluminescence (PL) spectra are employed to study the structural and optical property of both pure Rhodamine B (RHB) and samples absorbed on a kind of typical materials of institute lavoisier frameworks (MIL) under high pressure, respectively. The luminescence of RHB@MIL 53(Fe) can persist to pressures much higher than that for pure RHB. Our studies revealed that the PL emissions of RHB origin from monomeric and dimeric structures, respectively. Furthermore, our results indicated that the confining effect of MIL 53(Fe) pores inhibited the dimerization of RHB molecules under high pressure.

Enhancing Methylene Blue Dye Removal using pyrolyzed Mytella falcata Shells: Characterization, Kinetics, Isotherm, and Regeneration through Photolysis and Peroxidation.

The potential of pyrolyzed Mytella falcata shells as an adsorbent for removing methylene blue dye molecules from aqueous solutions was investigated. The study found that the adsorbent produced at 600 °C of pyrolysis temperature, with an adsorbent mass of 0.5 g, particle diameter of 0.297-0.149 mm, and pH 12.0, demonstrated the highest dye molecule removal efficiency of 82.41%. The material's porosity was observed through scanning electron microscopy, which is favorable for adsorption, while Fourier-transform infrared spectroscopy and X-Ray diffraction analysis analyses confirmed the presence of calcium carbonate in the crystalline phases. The pseudo-second order model was found to be the best fit for the data, suggesting that the adsorption mechanism involves two steps: external diffusion and diffusion via the solid pores. The Redlich-Peterson isotherm model better represented the equilibrium data, and the methylene blue adsorption was found to be spontaneous, favorable, and endothermic. The hydrogen peroxide with UV oxidation was found to be the most efficient method of regeneration, with a regeneration percentage of 63% achieved using 600 mmol.L-1 of oxidizing agents. The results suggest that pyrolyzed Mytella falcata shells could serve as an ecologically viable adsorbent alternative, reducing the amount of waste produced in the local environment and at the same time removing pollutants from the water. The material's adsorption capacity remained almost constant in the first adsorption-oxidation cycles, indicating its potential for repeated use.

A quantitative theory integrating solid surface hydrophilicity and pore structure features for non-phase-change drying of sewage sludge through gradient increase of ultrahigh filtration pressure

The sustainable application of thermal sludge drying process is limited by the high energy consumption due to the phase-change latent heat of moisture. This study proposed that the ultrahigh pressure filtration could realize the non-phase-change sludge drying. The lowest water content of 28.12 wt.% was realized by the filtration pressure of 21 MPa for the excess sludge with polyaluminium chloride as the conditioning agent. With the stepwise increase of filtration pressure employed (5-21 MPa), the diameter of solid pores was gradually narrowed to the same order of magnitude with the thickness of vicinal water film (i.e., 1-10 nm). As a result, the capillary water was transformed into the vicinal water, and the solid-water interface interaction played more crucial roles in water occurrence states. However, Hagen-Poiseuille equation was introduced to estimate the pore water outflow based on the pore wall hydrophilicity and the external filtration pressure, which implied that there can be always a sufficiently large driving force to maintain the water outflow rate no matter how the pore diameter is small and the sidewall is hydrophilic. Typically, the fitting results of excess sludge (R2=0.985, p-value<0.01) indicated that the pressure gradient of 2.11 × 109 Pa/m was required to maintain the pore water flow rate of 1.38 × 10−15 m3/s with the median pore diameter of 5.33 × 10−7 m. All these findings broke through the conventional cognition that only thermal drying process can decrease the sludge water content below 60 wt.%, and facilitated energy saving of sludge dewatering process through non-phase-change separation, i.e., ultrahigh pressure filtration.

Amphoteric composite of ZrP and N-doped porous carbon: Synthesis, characterization, and potential use for cycloaddition of CO2

Composites of amorphous ZrP and N-doped carbon were prepared in a one-step pyrolysis process instead of general post-loading technique. Owing to their mesoporous structure (6–10 nm) and Zr content (up to 41 wt%), the amphoteric materials have potential use in the cycloaddition of CO2 to epoxides, which is an acid‒base tandem process including the ring opening of epoxides and the addition of CO2. Substantial work has been done on how starting materials impact the structure and performance of composite materials. The coordination between metal and melamine has been confirmed, and it can be implanted in the melamine-polymer initiation of formation of porous metal-carbon materials. The composite catalysts exhibit amphoteric properties, present broad-spectrum adsorption, and finally produce carbonates via cycloaddition of CO2 to epoxides. It is remarkable that the multiple characteristics of porous solids are stabilized, and no significant loss of catalytic performance is observed after four cycles.

Rapid screening of gas solubility in ionic liquids using biased particle insertions with pre-sampled liquid trajectories

ABSTRACTWe present an efficient, general-purpose variant of the Widom test particle insertion method for computing chemical potentials of gaseous solutes in fluids or porous solids. The method is implemented in the Monte Carlo molecular simulation engine Cassandra, but receiving phase configurations are independent of this process and may be pre-sampled by other molecular simulation engines such as molecular dynamics codes. Efficiency enhancements present in this method include configurational biasing and accelerated atomic overlap detection. When applied to the estimation of Henry's law constants of atomistic difluoromethane and pentafluoroethane in ionic liquids, the accelerated overlap detection results in a speedup of more than an order of magnitude compared to conventional methods without sacrificing accuracy. We found good agreement between this method and Hamiltonian replica exchange (HREX) for Henry's law constant and absorption isotherm estimation. This embarrassingly parallel method is especially well suited for screening Henry's law constants of many small gases in the same solvents, since a liquid trajectory can be reused for as many solutes as desired.

A semi-implicit material point method for coupled thermo-hydro-mechanical simulation of saturated porous media in large deformation

The coupled thermo-hydro-mechanical (THM) response of liquid-infiltrated porous media underpins the safe operation and maintenance of key engineering infrastructure. Challenges remain in modeling and understanding the complicated multiphysics processes of porous media subjected to THM loads and undergoing large deformation. In this study, we develop a stabilized material point method (MPM) for modeling the THM responses of large deformation problems in biphasic solid–fluid mixtures. A novel and efficient staggered solution scheme is proposed to solve the governing equations of the coupled system formulated in terms of four primary variables: solid displacement (u), liquid velocity (v), pore pressure (p), and temperature (T). The scheme solves the energy balance equation first and employs the resulting temperature to further advance the calculation of the momentum and mass balance equations using a semi-implicit fractional step method to facilitate equal-order interpolations. Both the incompressible and weakly compressible fluid are considered in the presented fractional step formulations. We also develop the axisymmetric form of the coupled MPM to increase the applicability and efficiency of the method in THM problems. The validity, stability, and robustness of the proposed method are demonstrated through three benchmark problems, including the heating of a saturated half-space, the non-isothermal consolidation of a soil column, and a three-dimensional axisymmetric problem pertaining to the thermoelastic response around a point heat source. The predictive capability of the proposed method for large deformation problems is further showcased by the simulation of the progressive failure process of a thermal-sensitive slope.

Effects of the adsorbate-gas interface at the pore opening on the lower closure point in gaseous adsorption in porous solids

The limit to the lower closure point (LCP) observed experimentally in the desorption isotherm of gases in porous solids has been commonly attributed to the homogeneous cavitation of the condensate in cavities. It was proposed recently that the experimental limit to LCP could be described in simulations with the ink-bottle pore, provided that the length of the uniformly sized conduit connecting the closed cavity to the surrounding is shorter than 2 nm, and the evaporation is by way of pore blocking mechanism, rather than homogeneous cavitation. To substantiate this assertion, that deviates from the commonly belief of homogeneous cavitation, we further investigated in this paper with cavities having wedge-like pore opening, that better mimics real solids, and offer further explanation on the limit of the LCP to the pore blocking as the mechanism of evaporation with simulations of argon and nitrogen adsorption over a range of temperatures that are commonly used experimentally. It was found that simulation results correctly captured the experimental observations for carbon-based materials and silica-based materials in that the limit of LCP shifts to higher reduced pressures for weaker adsorbing silica, compared to stronger adsorbing carbon and for a given adsorbent it also shifts to higher reduced pressure for higher temperatures.

Porous Ionic Liquids Go Green.

This Perspective points toward pathways to prepare porous ionic liquids using easily accessible materials, aiming for reduced environmental impact. We demonstrate that suspensions of porous solids are stable in eutectic mixtures, underscoring their potential for the preparation of porous ionic liquids. Porous ionic liquids retain the wide electrochemical window observed in their precursor pure ionic liquids, rendering them well-suited for green electrochemical reactions, particularly those involving gases whose solubility is enhanced in the porous suspensions. Moreover, their capacity as gas-rich media points to sustainable biomedical and pharmaceutical applications, provided nontoxic, biocompatible ionic liquids and porous solids are utilized.

Stereolithography for manufacturing of advanced porous solids

The aim of this paper is focused on benefits of stereolithography (SLA) technology for the fabrication of the lightweight lattice structures with potential for load-bearing function and high absorption of impact energy. SLA is an additive manufacturing technology employing the principle of liquid resins curing moderated by radiation of a wavelength from ultra-violet band where resulting material parameters are tunable by setting of the curing process. The batches of samples manufactured using three different resins were subjected to quasi-static uni-axial tensile and compression tests. Acquired data were processed to derive deformation behaviour expressed as stress-strain diagrams and fundamental material properties. Based on the knowledge obtained from the mechanical tests, the setup of the fabrication parameters, the most suitable resin for manufacturing of the lattice structures and the overall suitability of SLA technology for the fabrication of advanced porous materials, were determined.

Macro and micro properties of the cement-based material mixed with coral powder and GGBFS under seawater condition

On island, the use of discarded coral reef is a way to resolve the lack of raw material for preparing concrete. Discarded coral reef can not only be used as aggregate, but be ground to powder to replace cement. Since the cement-based material prepared with discarded coral reef is exclusively used on island, the property of the cement-based material exposed to seawater condition should be studied. In this study, discarded coral reef is ground into coral powder (CP). CP is used together with ground granulated blast furnace slag (GGBFS) to replace Portland cement (PC) partially to prepare a mixture with good performance and the minimum use of PC. The compressive strength, solid phase composition and pore structure of the cement-based material exposed to seawater condition are investigated systematically. The results show that the addition of CP decreases the fluidity of the cement mortar since it has a more rough surface than other raw materials. Although the use of CP decreases the compressive strength of cement mortar, the coupled use of GGBFS can largely mitigate the strength loss of the cement mortar by comparing 9 mixtures. When the specimens are exposed to seawater, the strength of cement mortar only decreases slightly, but the pore structure of cement paste is densified. It suggests that the use of CP and GGBFS together in the concrete can meet the construction of island; the compressive strength of the sample made with 25% CP and 25% GGBFS is around 54 MPa after exposed to seawater to 1 year.

A Review: Study on the Enhancement Mechanism of Heat and Moisture Transfer in Deformable Porous Media

The heat and moisture transfer process in deformable porous media commonly exists in material drying, solid waste treatment, bioengineering, and so on. The transfer process is accompanied by deformation of the solid skeleton and pore interface structure, which limits the transfer rate and affects quality. Microwave and ultrasound are the main representatives of reinforcement technology. However, as the moisture decreases, the energy utilization efficiency of microwaves decreases significantly. Based on the experimental and theoretical methods, the enhancement mechanism of ultrasound on the process is studied, which provides guidance for the wide application of ultrasonic enhancement. With the increase in ultrasound power, the pore area and the moisture effective diffusion coefficient gradually increase. A macroscope mathematical model for ultrasonic-coupled thermal-hydro-mechanical modeling is developed, and the results show that ultrasound increases the temperature gradient within material, resulting in higher moisture transmission rates with an ordered direction, and the alternating expansion and compression process results in smaller macroscopic deformations. Subsequently, the drying kinetic characteristics of typical deformable porous media such as municipal sludge, porous fibers, and activated alumina particles are investigated. The process parameters of the ultrasonic assisted drying system are optimized using the response surface method and artificial neural network model.

Effect of solid content on the piezoelectric properties of porous (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 ceramics

The influence of the solid content of porous (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT) ceramics on the pore morphology and mechanical and piezoelectric properties was systematically investigated. The results show that with an increase in solid content, porosity and pore size decreased, and ceramic connectivity increased, leading to an increase in compressive strength. The best ferroelectric performance was achieved with an Ec of 2.40 kV/cm2 and a Pr of 2.01 μC/cm2 at a solid content of 30 vol%. When the solid content increased, the relative dielectric constant and the piezoelectric constant increased, which affected the piezoelectric energy harvesting performance. At a solid content of 20 vol%, g33 and FOM33 reached maxima of 43 × 10−3 Vm/N and 6.7 p.m.2/N, which were 2.40 times and 1.8 times those of the other solid contents, respectively. This work provides new ideas for the design of porous piezoelectric ceramics and the improvement of their piezoelectric properties for future piezoelectric energy harvesting applications.