...
        I2C_InitStruct.I2C_Mode =I2C_Mode_I2C;
    I2C_InitStruct.I2C_OwnAddress1=0x2a; <<<<
    I2C_InitStruct.I2C_Ack=I2C_Ack_Enable;
    I2C_InitStruct.I2C_DutyCycle=I2C_DutyCycle_2;
    I2C_InitStruct.I2C_ClockSpeed = 100000;
    I2C_InitStruct.I2C_AcknowledgedAddress=I2C_AcknowledgedAddress_7bit; <<<< //0x4000
    I2C_Init(I2C1, &I2C_InitStruct);
....

I2Cx->OAR1 = (I2C_InitStruct->I2C_AcknowledgedAddress | I2C_InitStruct->I2C_OwnAddress1);

int main(void)
{
    union {
        int word;
        struct {
            int add0:1;
            int add7:6;
        } fields;
    } demo;

    demo.word = 0x2a;

    printf("add7 %#x\n", demo.fields.add7);
    return 0;
}

typedef struct
{
  uint32_t I2C_ClockSpeed;          /*!< Specifies the clock frequency.
                                         This parameter must be set to a value lower than 400kHz */

  uint16_t I2C_Mode;                /*!< Specifies the I2C mode.
                                         This parameter can be a value of @ref I2C_mode */

  uint16_t I2C_DutyCycle;           /*!< Specifies the I2C fast mode duty cycle.
                                         This parameter can be a value of @ref I2C_duty_cycle_in_fast_mode */

  uint16_t I2C_OwnAddress1;         /*!< Specifies the first device own address.
                                         This parameter can be a 7-bit or 10-bit address. */

  uint16_t I2C_Ack;                 /*!< Enables or disables the acknowledgement.
                                         This parameter can be a value of @ref I2C_acknowledgement */

  uint16_t I2C_AcknowledgedAddress; /*!< Specifies if 7-bit or 10-bit address is acknowledged.
                                         This parameter can be a value of @ref I2C_acknowledged_address */
}I2C_InitTypeDef;