Giving Zakaat To A Masjid

For the validity of one’s Zakaat, it is necessary that the Zakaat be given in the ownership of  a poor person that qualifies as a recipient of Zakaat. Fulfilling this requirement is not possible when donating one’s Zakaat to a Masjid hence it will not be  permissible to donate one’s Zakaat to a Masjid. 

Yes, if donated to a recipient of Zakaat and he voluntarily donates it to a Masjid thereafter, then there is no harm in doing so.