Polymer‐Derived Silicoboron Carbonitride Foams for CO₂ Capture: From Design to Application as Scaffolds for the in Situ Growth of Metal–Organic Frameworks

Abstract

A template-assisted polymer-derived ceramic route is investigated for preparing a series of silicoboron carbonitride (Si/B/C/N) foams with a hierarchical pore size distribution and tailorable interconnected porosity. A boron-modified polycarbosilazane was selected to impregnate monolithic silica and carbonaceous templates and form after pyrolysis and template removal Si/B/C/N foams. By changing the hard template nature and controlling the quantity of polymer to be impregnated, controlled micropore/macropore distributions with mesoscopic cell windows are generated. Specific surface areas from 29 to 239 m(2) g(-1) and porosities from 51 to 77 % are achieved. These foams combine a low density with a thermal insulation and a relatively good thermostructural stability. Their particular structure allowed the in situ growth of metal-organic frameworks (MOFs) directly within the open-cell structure. MOFs offered a microporosity feature to the resulting Si/B/C/N@MOF composite foams that allowed increasing the specific surface area to provide CO2 uptake of 2.2 %.

Molecular‐Level Processing of Si‐(B)‐C Materials with Tailored Nano/Microstructures

“…Similarly to AHPCS, such samples can be used in solutions for coating substrates by dip‐ or spin‐coating. They can also be used in exo ‐templating processes to form ceramics of controlled porosities, as we reported in previous papers for other materials . As an illustration, the PBCS 200 sample displays a sufficient solubility (for instance in toluene) to impregnate carbonaceous foams, labeled as 4F5HF (Figure ).…”

Hierarchical Metal–Organic Frameworks with Macroporosity: Synthesis, Achievements, and Challenges

“…Hard templates may be carbons [62], ceramics [59,61,[63][64][65], and metals [60,[66][67][68]). They are typically in the form of monoliths, porous membranes, or foams [60,62,69].…”

“…Thus, they are preferentially used in some applications that require easy integration and regeneration (e.g. for adsorbent systems [ 59 , 60 ]) or exceptional mass transfer (e.g. for catalyst supports [ 61 ]).…”

“…The excellent electrocatalytic activity was attributed to the presence of macropores in the hierarchical structure which was led to improved mass transfer of the glucose. Using a similar hard template, Sandra et al [ 59 ] synthesised a series of silicoboron carbonitride (Si/B/C/N) polymer-derived ceramic (PDC) foams with micro-/macroporosity using silicon and carbon high internal phase emulsions (HIPE) as exo templates and boron-modified polycarbosilazane as an organosilicon precursor. HKUST-1 was impregnated by growing the MOF inside the macropores of the PDC to form Si/B/C/N@MOF composite foams, allowing faster and more efficient uptake and release kinetics, in particular for CO 2 capture.…”

Using Supercritical CO2 in the Preparation of Metal-Organic Frameworks: Investigating Effects on Crystallisation

“…Due to the high interest in these materials, various synthetic methods have been developed beyond the conventional solvothermal approaches which, though a straightforward way to achieve highly crystalline materials, have the potential to use large amounts of organic solvents. In addition, there has been a recent trend towards the creation of multiple porosities (so-called hierarchical pore structures) in these materials [23,24], leading to the development of a number of innovative synthetic strategies including macrostructural templating [25][26][27][28][29], gelation [30][31][32][33], acid etching [34][35][36][37], use of scCO 2 [38][39][40][41][42], and three-dimensional (3D) printing [43][44][45][46].…”