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Cu 4 I 4 cubane-type secondary building units are reticulated with a piperazine linker at room temperature to crystallize the metal-organic frameworks (MOFs) Cu 4 I 4 (Pip) 2 in a non-centrosymmetric P 6 2 22 space group. For the first time, cubane cluster type MOF's strong piezoelectric nature has been studied by switching spectroscopy piezo force microscopy (SS-PFM) and piezo force microscopy (PFM) mapping of the crystal, with piezoelectric constant ( d 33 ) ∼52.33 pm V -1 , highlighting its potential for mechanical energy harvesting processes.

Conjugated and processable self-standing vinylene-linked covalent organic framework membranes (COFMs) are highly demanding for photonics and optoelectronics. In this work, we have fabricated the first cyclotriphosphazene (CTP) cored vinylene-linked self-standing COFM (CTP-PDAN). For comparison purposes, we have successfully fabricated the imine-linked congener (CTP-PDA). Leveraging the inherent nonlinear optical (NLO) response of the CTP core, both membranes were directly mounted to evaluate NLO parameters using the open-aperture (OA) Z-scan technique. Direct measurement of NLO responses on membranes is advantageous and free from solvent and scattering effects, making it a more practical approach compared to the conventional dispersion mode. The OA Z-scan transmission yields a reverse saturable absorption signature exhibiting a higher NLO absorption coefficient (β) of 58.37 cm/GW for CTP-PDAN, compared to that of the imine-linked CTP-PDA COFM (β = 8.5 cm/GW). These results can be correlated to the efficient conjugation through the vinylene linkage in CTP-PDAN compared to the imine linked congener.